Update build-tools to ab/7064006

https://ci.android.com/builds/branches/aosp-build-tools-release/grid?head=7064006&tail=7064006

Test: treehugger
Change-Id: I4fa4337a1f9c5a347d34725fa4d3cb7256043c98
diff --git a/common/py3-stdlib/importlib/__init__.py b/common/py3-stdlib/importlib/__init__.py
new file mode 100644
index 0000000..0c73c50
--- /dev/null
+++ b/common/py3-stdlib/importlib/__init__.py
@@ -0,0 +1,176 @@
+"""A pure Python implementation of import."""
+__all__ = ['__import__', 'import_module', 'invalidate_caches', 'reload']
+
+# Bootstrap help #####################################################
+
+# Until bootstrapping is complete, DO NOT import any modules that attempt
+# to import importlib._bootstrap (directly or indirectly). Since this
+# partially initialised package would be present in sys.modules, those
+# modules would get an uninitialised copy of the source version, instead
+# of a fully initialised version (either the frozen one or the one
+# initialised below if the frozen one is not available).
+import _imp  # Just the builtin component, NOT the full Python module
+import sys
+
+try:
+    import _frozen_importlib as _bootstrap
+except ImportError:
+    from . import _bootstrap
+    _bootstrap._setup(sys, _imp)
+else:
+    # importlib._bootstrap is the built-in import, ensure we don't create
+    # a second copy of the module.
+    _bootstrap.__name__ = 'importlib._bootstrap'
+    _bootstrap.__package__ = 'importlib'
+    try:
+        _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
+    except NameError:
+        # __file__ is not guaranteed to be defined, e.g. if this code gets
+        # frozen by a tool like cx_Freeze.
+        pass
+    sys.modules['importlib._bootstrap'] = _bootstrap
+
+try:
+    import _frozen_importlib_external as _bootstrap_external
+except ImportError:
+    from . import _bootstrap_external
+    _bootstrap_external._setup(_bootstrap)
+    _bootstrap._bootstrap_external = _bootstrap_external
+else:
+    _bootstrap_external.__name__ = 'importlib._bootstrap_external'
+    _bootstrap_external.__package__ = 'importlib'
+    try:
+        _bootstrap_external.__file__ = __file__.replace('__init__.py', '_bootstrap_external.py')
+    except NameError:
+        # __file__ is not guaranteed to be defined, e.g. if this code gets
+        # frozen by a tool like cx_Freeze.
+        pass
+    sys.modules['importlib._bootstrap_external'] = _bootstrap_external
+
+# To simplify imports in test code
+_pack_uint32 = _bootstrap_external._pack_uint32
+_unpack_uint32 = _bootstrap_external._unpack_uint32
+
+# Fully bootstrapped at this point, import whatever you like, circular
+# dependencies and startup overhead minimisation permitting :)
+
+import types
+import warnings
+
+
+# Public API #########################################################
+
+from ._bootstrap import __import__
+
+
+def invalidate_caches():
+    """Call the invalidate_caches() method on all meta path finders stored in
+    sys.meta_path (where implemented)."""
+    for finder in sys.meta_path:
+        if hasattr(finder, 'invalidate_caches'):
+            finder.invalidate_caches()
+
+
+def find_loader(name, path=None):
+    """Return the loader for the specified module.
+
+    This is a backward-compatible wrapper around find_spec().
+
+    This function is deprecated in favor of importlib.util.find_spec().
+
+    """
+    warnings.warn('Deprecated since Python 3.4. '
+                  'Use importlib.util.find_spec() instead.',
+                  DeprecationWarning, stacklevel=2)
+    try:
+        loader = sys.modules[name].__loader__
+        if loader is None:
+            raise ValueError('{}.__loader__ is None'.format(name))
+        else:
+            return loader
+    except KeyError:
+        pass
+    except AttributeError:
+        raise ValueError('{}.__loader__ is not set'.format(name)) from None
+
+    spec = _bootstrap._find_spec(name, path)
+    # We won't worry about malformed specs (missing attributes).
+    if spec is None:
+        return None
+    if spec.loader is None:
+        if spec.submodule_search_locations is None:
+            raise ImportError('spec for {} missing loader'.format(name),
+                              name=name)
+        raise ImportError('namespace packages do not have loaders',
+                          name=name)
+    return spec.loader
+
+
+def import_module(name, package=None):
+    """Import a module.
+
+    The 'package' argument is required when performing a relative import. It
+    specifies the package to use as the anchor point from which to resolve the
+    relative import to an absolute import.
+
+    """
+    level = 0
+    if name.startswith('.'):
+        if not package:
+            msg = ("the 'package' argument is required to perform a relative "
+                   "import for {!r}")
+            raise TypeError(msg.format(name))
+        for character in name:
+            if character != '.':
+                break
+            level += 1
+    return _bootstrap._gcd_import(name[level:], package, level)
+
+
+_RELOADING = {}
+
+
+def reload(module):
+    """Reload the module and return it.
+
+    The module must have been successfully imported before.
+
+    """
+    if not module or not isinstance(module, types.ModuleType):
+        raise TypeError("reload() argument must be a module")
+    try:
+        name = module.__spec__.name
+    except AttributeError:
+        name = module.__name__
+
+    if sys.modules.get(name) is not module:
+        msg = "module {} not in sys.modules"
+        raise ImportError(msg.format(name), name=name)
+    if name in _RELOADING:
+        return _RELOADING[name]
+    _RELOADING[name] = module
+    try:
+        parent_name = name.rpartition('.')[0]
+        if parent_name:
+            try:
+                parent = sys.modules[parent_name]
+            except KeyError:
+                msg = "parent {!r} not in sys.modules"
+                raise ImportError(msg.format(parent_name),
+                                  name=parent_name) from None
+            else:
+                pkgpath = parent.__path__
+        else:
+            pkgpath = None
+        target = module
+        spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
+        if spec is None:
+            raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
+        _bootstrap._exec(spec, module)
+        # The module may have replaced itself in sys.modules!
+        return sys.modules[name]
+    finally:
+        try:
+            del _RELOADING[name]
+        except KeyError:
+            pass
diff --git a/common/py3-stdlib/importlib/_bootstrap.py b/common/py3-stdlib/importlib/_bootstrap.py
new file mode 100644
index 0000000..32deef1
--- /dev/null
+++ b/common/py3-stdlib/importlib/_bootstrap.py
@@ -0,0 +1,1173 @@
+"""Core implementation of import.
+
+This module is NOT meant to be directly imported! It has been designed such
+that it can be bootstrapped into Python as the implementation of import. As
+such it requires the injection of specific modules and attributes in order to
+work. One should use importlib as the public-facing version of this module.
+
+"""
+#
+# IMPORTANT: Whenever making changes to this module, be sure to run a top-level
+# `make regen-importlib` followed by `make` in order to get the frozen version
+# of the module updated. Not doing so will result in the Makefile to fail for
+# all others who don't have a ./python around to freeze the module
+# in the early stages of compilation.
+#
+
+# See importlib._setup() for what is injected into the global namespace.
+
+# When editing this code be aware that code executed at import time CANNOT
+# reference any injected objects! This includes not only global code but also
+# anything specified at the class level.
+
+# Bootstrap-related code ######################################################
+
+_bootstrap_external = None
+
+def _wrap(new, old):
+    """Simple substitute for functools.update_wrapper."""
+    for replace in ['__module__', '__name__', '__qualname__', '__doc__']:
+        if hasattr(old, replace):
+            setattr(new, replace, getattr(old, replace))
+    new.__dict__.update(old.__dict__)
+
+
+def _new_module(name):
+    return type(sys)(name)
+
+
+# Module-level locking ########################################################
+
+# A dict mapping module names to weakrefs of _ModuleLock instances
+# Dictionary protected by the global import lock
+_module_locks = {}
+# A dict mapping thread ids to _ModuleLock instances
+_blocking_on = {}
+
+
+class _DeadlockError(RuntimeError):
+    pass
+
+
+class _ModuleLock:
+    """A recursive lock implementation which is able to detect deadlocks
+    (e.g. thread 1 trying to take locks A then B, and thread 2 trying to
+    take locks B then A).
+    """
+
+    def __init__(self, name):
+        self.lock = _thread.allocate_lock()
+        self.wakeup = _thread.allocate_lock()
+        self.name = name
+        self.owner = None
+        self.count = 0
+        self.waiters = 0
+
+    def has_deadlock(self):
+        # Deadlock avoidance for concurrent circular imports.
+        me = _thread.get_ident()
+        tid = self.owner
+        while True:
+            lock = _blocking_on.get(tid)
+            if lock is None:
+                return False
+            tid = lock.owner
+            if tid == me:
+                return True
+
+    def acquire(self):
+        """
+        Acquire the module lock.  If a potential deadlock is detected,
+        a _DeadlockError is raised.
+        Otherwise, the lock is always acquired and True is returned.
+        """
+        tid = _thread.get_ident()
+        _blocking_on[tid] = self
+        try:
+            while True:
+                with self.lock:
+                    if self.count == 0 or self.owner == tid:
+                        self.owner = tid
+                        self.count += 1
+                        return True
+                    if self.has_deadlock():
+                        raise _DeadlockError('deadlock detected by %r' % self)
+                    if self.wakeup.acquire(False):
+                        self.waiters += 1
+                # Wait for a release() call
+                self.wakeup.acquire()
+                self.wakeup.release()
+        finally:
+            del _blocking_on[tid]
+
+    def release(self):
+        tid = _thread.get_ident()
+        with self.lock:
+            if self.owner != tid:
+                raise RuntimeError('cannot release un-acquired lock')
+            assert self.count > 0
+            self.count -= 1
+            if self.count == 0:
+                self.owner = None
+                if self.waiters:
+                    self.waiters -= 1
+                    self.wakeup.release()
+
+    def __repr__(self):
+        return '_ModuleLock({!r}) at {}'.format(self.name, id(self))
+
+
+class _DummyModuleLock:
+    """A simple _ModuleLock equivalent for Python builds without
+    multi-threading support."""
+
+    def __init__(self, name):
+        self.name = name
+        self.count = 0
+
+    def acquire(self):
+        self.count += 1
+        return True
+
+    def release(self):
+        if self.count == 0:
+            raise RuntimeError('cannot release un-acquired lock')
+        self.count -= 1
+
+    def __repr__(self):
+        return '_DummyModuleLock({!r}) at {}'.format(self.name, id(self))
+
+
+class _ModuleLockManager:
+
+    def __init__(self, name):
+        self._name = name
+        self._lock = None
+
+    def __enter__(self):
+        self._lock = _get_module_lock(self._name)
+        self._lock.acquire()
+
+    def __exit__(self, *args, **kwargs):
+        self._lock.release()
+
+
+# The following two functions are for consumption by Python/import.c.
+
+def _get_module_lock(name):
+    """Get or create the module lock for a given module name.
+
+    Acquire/release internally the global import lock to protect
+    _module_locks."""
+
+    _imp.acquire_lock()
+    try:
+        try:
+            lock = _module_locks[name]()
+        except KeyError:
+            lock = None
+
+        if lock is None:
+            if _thread is None:
+                lock = _DummyModuleLock(name)
+            else:
+                lock = _ModuleLock(name)
+
+            def cb(ref, name=name):
+                _imp.acquire_lock()
+                try:
+                    # bpo-31070: Check if another thread created a new lock
+                    # after the previous lock was destroyed
+                    # but before the weakref callback was called.
+                    if _module_locks.get(name) is ref:
+                        del _module_locks[name]
+                finally:
+                    _imp.release_lock()
+
+            _module_locks[name] = _weakref.ref(lock, cb)
+    finally:
+        _imp.release_lock()
+
+    return lock
+
+
+def _lock_unlock_module(name):
+    """Acquires then releases the module lock for a given module name.
+
+    This is used to ensure a module is completely initialized, in the
+    event it is being imported by another thread.
+    """
+    lock = _get_module_lock(name)
+    try:
+        lock.acquire()
+    except _DeadlockError:
+        # Concurrent circular import, we'll accept a partially initialized
+        # module object.
+        pass
+    else:
+        lock.release()
+
+# Frame stripping magic ###############################################
+def _call_with_frames_removed(f, *args, **kwds):
+    """remove_importlib_frames in import.c will always remove sequences
+    of importlib frames that end with a call to this function
+
+    Use it instead of a normal call in places where including the importlib
+    frames introduces unwanted noise into the traceback (e.g. when executing
+    module code)
+    """
+    return f(*args, **kwds)
+
+
+def _verbose_message(message, *args, verbosity=1):
+    """Print the message to stderr if -v/PYTHONVERBOSE is turned on."""
+    if sys.flags.verbose >= verbosity:
+        if not message.startswith(('#', 'import ')):
+            message = '# ' + message
+        print(message.format(*args), file=sys.stderr)
+
+
+def _requires_builtin(fxn):
+    """Decorator to verify the named module is built-in."""
+    def _requires_builtin_wrapper(self, fullname):
+        if fullname not in sys.builtin_module_names:
+            raise ImportError('{!r} is not a built-in module'.format(fullname),
+                              name=fullname)
+        return fxn(self, fullname)
+    _wrap(_requires_builtin_wrapper, fxn)
+    return _requires_builtin_wrapper
+
+
+def _requires_frozen(fxn):
+    """Decorator to verify the named module is frozen."""
+    def _requires_frozen_wrapper(self, fullname):
+        if not _imp.is_frozen(fullname):
+            raise ImportError('{!r} is not a frozen module'.format(fullname),
+                              name=fullname)
+        return fxn(self, fullname)
+    _wrap(_requires_frozen_wrapper, fxn)
+    return _requires_frozen_wrapper
+
+
+# Typically used by loader classes as a method replacement.
+def _load_module_shim(self, fullname):
+    """Load the specified module into sys.modules and return it.
+
+    This method is deprecated.  Use loader.exec_module instead.
+
+    """
+    spec = spec_from_loader(fullname, self)
+    if fullname in sys.modules:
+        module = sys.modules[fullname]
+        _exec(spec, module)
+        return sys.modules[fullname]
+    else:
+        return _load(spec)
+
+# Module specifications #######################################################
+
+def _module_repr(module):
+    # The implementation of ModuleType.__repr__().
+    loader = getattr(module, '__loader__', None)
+    if hasattr(loader, 'module_repr'):
+        # As soon as BuiltinImporter, FrozenImporter, and NamespaceLoader
+        # drop their implementations for module_repr. we can add a
+        # deprecation warning here.
+        try:
+            return loader.module_repr(module)
+        except Exception:
+            pass
+    try:
+        spec = module.__spec__
+    except AttributeError:
+        pass
+    else:
+        if spec is not None:
+            return _module_repr_from_spec(spec)
+
+    # We could use module.__class__.__name__ instead of 'module' in the
+    # various repr permutations.
+    try:
+        name = module.__name__
+    except AttributeError:
+        name = '?'
+    try:
+        filename = module.__file__
+    except AttributeError:
+        if loader is None:
+            return '<module {!r}>'.format(name)
+        else:
+            return '<module {!r} ({!r})>'.format(name, loader)
+    else:
+        return '<module {!r} from {!r}>'.format(name, filename)
+
+
+class ModuleSpec:
+    """The specification for a module, used for loading.
+
+    A module's spec is the source for information about the module.  For
+    data associated with the module, including source, use the spec's
+    loader.
+
+    `name` is the absolute name of the module.  `loader` is the loader
+    to use when loading the module.  `parent` is the name of the
+    package the module is in.  The parent is derived from the name.
+
+    `is_package` determines if the module is considered a package or
+    not.  On modules this is reflected by the `__path__` attribute.
+
+    `origin` is the specific location used by the loader from which to
+    load the module, if that information is available.  When filename is
+    set, origin will match.
+
+    `has_location` indicates that a spec's "origin" reflects a location.
+    When this is True, `__file__` attribute of the module is set.
+
+    `cached` is the location of the cached bytecode file, if any.  It
+    corresponds to the `__cached__` attribute.
+
+    `submodule_search_locations` is the sequence of path entries to
+    search when importing submodules.  If set, is_package should be
+    True--and False otherwise.
+
+    Packages are simply modules that (may) have submodules.  If a spec
+    has a non-None value in `submodule_search_locations`, the import
+    system will consider modules loaded from the spec as packages.
+
+    Only finders (see importlib.abc.MetaPathFinder and
+    importlib.abc.PathEntryFinder) should modify ModuleSpec instances.
+
+    """
+
+    def __init__(self, name, loader, *, origin=None, loader_state=None,
+                 is_package=None):
+        self.name = name
+        self.loader = loader
+        self.origin = origin
+        self.loader_state = loader_state
+        self.submodule_search_locations = [] if is_package else None
+
+        # file-location attributes
+        self._set_fileattr = False
+        self._cached = None
+
+    def __repr__(self):
+        args = ['name={!r}'.format(self.name),
+                'loader={!r}'.format(self.loader)]
+        if self.origin is not None:
+            args.append('origin={!r}'.format(self.origin))
+        if self.submodule_search_locations is not None:
+            args.append('submodule_search_locations={}'
+                        .format(self.submodule_search_locations))
+        return '{}({})'.format(self.__class__.__name__, ', '.join(args))
+
+    def __eq__(self, other):
+        smsl = self.submodule_search_locations
+        try:
+            return (self.name == other.name and
+                    self.loader == other.loader and
+                    self.origin == other.origin and
+                    smsl == other.submodule_search_locations and
+                    self.cached == other.cached and
+                    self.has_location == other.has_location)
+        except AttributeError:
+            return False
+
+    @property
+    def cached(self):
+        if self._cached is None:
+            if self.origin is not None and self._set_fileattr:
+                if _bootstrap_external is None:
+                    raise NotImplementedError
+                self._cached = _bootstrap_external._get_cached(self.origin)
+        return self._cached
+
+    @cached.setter
+    def cached(self, cached):
+        self._cached = cached
+
+    @property
+    def parent(self):
+        """The name of the module's parent."""
+        if self.submodule_search_locations is None:
+            return self.name.rpartition('.')[0]
+        else:
+            return self.name
+
+    @property
+    def has_location(self):
+        return self._set_fileattr
+
+    @has_location.setter
+    def has_location(self, value):
+        self._set_fileattr = bool(value)
+
+
+def spec_from_loader(name, loader, *, origin=None, is_package=None):
+    """Return a module spec based on various loader methods."""
+    if hasattr(loader, 'get_filename'):
+        if _bootstrap_external is None:
+            raise NotImplementedError
+        spec_from_file_location = _bootstrap_external.spec_from_file_location
+
+        if is_package is None:
+            return spec_from_file_location(name, loader=loader)
+        search = [] if is_package else None
+        return spec_from_file_location(name, loader=loader,
+                                       submodule_search_locations=search)
+
+    if is_package is None:
+        if hasattr(loader, 'is_package'):
+            try:
+                is_package = loader.is_package(name)
+            except ImportError:
+                is_package = None  # aka, undefined
+        else:
+            # the default
+            is_package = False
+
+    return ModuleSpec(name, loader, origin=origin, is_package=is_package)
+
+
+def _spec_from_module(module, loader=None, origin=None):
+    # This function is meant for use in _setup().
+    try:
+        spec = module.__spec__
+    except AttributeError:
+        pass
+    else:
+        if spec is not None:
+            return spec
+
+    name = module.__name__
+    if loader is None:
+        try:
+            loader = module.__loader__
+        except AttributeError:
+            # loader will stay None.
+            pass
+    try:
+        location = module.__file__
+    except AttributeError:
+        location = None
+    if origin is None:
+        if location is None:
+            try:
+                origin = loader._ORIGIN
+            except AttributeError:
+                origin = None
+        else:
+            origin = location
+    try:
+        cached = module.__cached__
+    except AttributeError:
+        cached = None
+    try:
+        submodule_search_locations = list(module.__path__)
+    except AttributeError:
+        submodule_search_locations = None
+
+    spec = ModuleSpec(name, loader, origin=origin)
+    spec._set_fileattr = False if location is None else True
+    spec.cached = cached
+    spec.submodule_search_locations = submodule_search_locations
+    return spec
+
+
+def _init_module_attrs(spec, module, *, override=False):
+    # The passed-in module may be not support attribute assignment,
+    # in which case we simply don't set the attributes.
+    # __name__
+    if (override or getattr(module, '__name__', None) is None):
+        try:
+            module.__name__ = spec.name
+        except AttributeError:
+            pass
+    # __loader__
+    if override or getattr(module, '__loader__', None) is None:
+        loader = spec.loader
+        if loader is None:
+            # A backward compatibility hack.
+            if spec.submodule_search_locations is not None:
+                if _bootstrap_external is None:
+                    raise NotImplementedError
+                _NamespaceLoader = _bootstrap_external._NamespaceLoader
+
+                loader = _NamespaceLoader.__new__(_NamespaceLoader)
+                loader._path = spec.submodule_search_locations
+                spec.loader = loader
+                # While the docs say that module.__file__ is not set for
+                # built-in modules, and the code below will avoid setting it if
+                # spec.has_location is false, this is incorrect for namespace
+                # packages.  Namespace packages have no location, but their
+                # __spec__.origin is None, and thus their module.__file__
+                # should also be None for consistency.  While a bit of a hack,
+                # this is the best place to ensure this consistency.
+                #
+                # See # https://docs.python.org/3/library/importlib.html#importlib.abc.Loader.load_module
+                # and bpo-32305
+                module.__file__ = None
+        try:
+            module.__loader__ = loader
+        except AttributeError:
+            pass
+    # __package__
+    if override or getattr(module, '__package__', None) is None:
+        try:
+            module.__package__ = spec.parent
+        except AttributeError:
+            pass
+    # __spec__
+    try:
+        module.__spec__ = spec
+    except AttributeError:
+        pass
+    # __path__
+    if override or getattr(module, '__path__', None) is None:
+        if spec.submodule_search_locations is not None:
+            try:
+                module.__path__ = spec.submodule_search_locations
+            except AttributeError:
+                pass
+    # __file__/__cached__
+    if spec.has_location:
+        if override or getattr(module, '__file__', None) is None:
+            try:
+                module.__file__ = spec.origin
+            except AttributeError:
+                pass
+
+        if override or getattr(module, '__cached__', None) is None:
+            if spec.cached is not None:
+                try:
+                    module.__cached__ = spec.cached
+                except AttributeError:
+                    pass
+    return module
+
+
+def module_from_spec(spec):
+    """Create a module based on the provided spec."""
+    # Typically loaders will not implement create_module().
+    module = None
+    if hasattr(spec.loader, 'create_module'):
+        # If create_module() returns `None` then it means default
+        # module creation should be used.
+        module = spec.loader.create_module(spec)
+    elif hasattr(spec.loader, 'exec_module'):
+        raise ImportError('loaders that define exec_module() '
+                          'must also define create_module()')
+    if module is None:
+        module = _new_module(spec.name)
+    _init_module_attrs(spec, module)
+    return module
+
+
+def _module_repr_from_spec(spec):
+    """Return the repr to use for the module."""
+    # We mostly replicate _module_repr() using the spec attributes.
+    name = '?' if spec.name is None else spec.name
+    if spec.origin is None:
+        if spec.loader is None:
+            return '<module {!r}>'.format(name)
+        else:
+            return '<module {!r} ({!r})>'.format(name, spec.loader)
+    else:
+        if spec.has_location:
+            return '<module {!r} from {!r}>'.format(name, spec.origin)
+        else:
+            return '<module {!r} ({})>'.format(spec.name, spec.origin)
+
+
+# Used by importlib.reload() and _load_module_shim().
+def _exec(spec, module):
+    """Execute the spec's specified module in an existing module's namespace."""
+    name = spec.name
+    with _ModuleLockManager(name):
+        if sys.modules.get(name) is not module:
+            msg = 'module {!r} not in sys.modules'.format(name)
+            raise ImportError(msg, name=name)
+        try:
+            if spec.loader is None:
+                if spec.submodule_search_locations is None:
+                    raise ImportError('missing loader', name=spec.name)
+                # Namespace package.
+                _init_module_attrs(spec, module, override=True)
+            else:
+                _init_module_attrs(spec, module, override=True)
+                if not hasattr(spec.loader, 'exec_module'):
+                    # (issue19713) Once BuiltinImporter and ExtensionFileLoader
+                    # have exec_module() implemented, we can add a deprecation
+                    # warning here.
+                    spec.loader.load_module(name)
+                else:
+                    spec.loader.exec_module(module)
+        finally:
+            # Update the order of insertion into sys.modules for module
+            # clean-up at shutdown.
+            module = sys.modules.pop(spec.name)
+            sys.modules[spec.name] = module
+    return module
+
+
+def _load_backward_compatible(spec):
+    # (issue19713) Once BuiltinImporter and ExtensionFileLoader
+    # have exec_module() implemented, we can add a deprecation
+    # warning here.
+    try:
+        spec.loader.load_module(spec.name)
+    except:
+        if spec.name in sys.modules:
+            module = sys.modules.pop(spec.name)
+            sys.modules[spec.name] = module
+        raise
+    # The module must be in sys.modules at this point!
+    # Move it to the end of sys.modules.
+    module = sys.modules.pop(spec.name)
+    sys.modules[spec.name] = module
+    if getattr(module, '__loader__', None) is None:
+        try:
+            module.__loader__ = spec.loader
+        except AttributeError:
+            pass
+    if getattr(module, '__package__', None) is None:
+        try:
+            # Since module.__path__ may not line up with
+            # spec.submodule_search_paths, we can't necessarily rely
+            # on spec.parent here.
+            module.__package__ = module.__name__
+            if not hasattr(module, '__path__'):
+                module.__package__ = spec.name.rpartition('.')[0]
+        except AttributeError:
+            pass
+    if getattr(module, '__spec__', None) is None:
+        try:
+            module.__spec__ = spec
+        except AttributeError:
+            pass
+    return module
+
+def _load_unlocked(spec):
+    # A helper for direct use by the import system.
+    if spec.loader is not None:
+        # Not a namespace package.
+        if not hasattr(spec.loader, 'exec_module'):
+            return _load_backward_compatible(spec)
+
+    module = module_from_spec(spec)
+
+    # This must be done before putting the module in sys.modules
+    # (otherwise an optimization shortcut in import.c becomes
+    # wrong).
+    spec._initializing = True
+    try:
+        sys.modules[spec.name] = module
+        try:
+            if spec.loader is None:
+                if spec.submodule_search_locations is None:
+                    raise ImportError('missing loader', name=spec.name)
+                # A namespace package so do nothing.
+            else:
+                spec.loader.exec_module(module)
+        except:
+            try:
+                del sys.modules[spec.name]
+            except KeyError:
+                pass
+            raise
+        # Move the module to the end of sys.modules.
+        # We don't ensure that the import-related module attributes get
+        # set in the sys.modules replacement case.  Such modules are on
+        # their own.
+        module = sys.modules.pop(spec.name)
+        sys.modules[spec.name] = module
+        _verbose_message('import {!r} # {!r}', spec.name, spec.loader)
+    finally:
+        spec._initializing = False
+
+    return module
+
+# A method used during testing of _load_unlocked() and by
+# _load_module_shim().
+def _load(spec):
+    """Return a new module object, loaded by the spec's loader.
+
+    The module is not added to its parent.
+
+    If a module is already in sys.modules, that existing module gets
+    clobbered.
+
+    """
+    with _ModuleLockManager(spec.name):
+        return _load_unlocked(spec)
+
+
+# Loaders #####################################################################
+
+class BuiltinImporter:
+
+    """Meta path import for built-in modules.
+
+    All methods are either class or static methods to avoid the need to
+    instantiate the class.
+
+    """
+
+    @staticmethod
+    def module_repr(module):
+        """Return repr for the module.
+
+        The method is deprecated.  The import machinery does the job itself.
+
+        """
+        return '<module {!r} (built-in)>'.format(module.__name__)
+
+    @classmethod
+    def find_spec(cls, fullname, path=None, target=None):
+        if path is not None:
+            return None
+        if _imp.is_builtin(fullname):
+            return spec_from_loader(fullname, cls, origin='built-in')
+        else:
+            return None
+
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        """Find the built-in module.
+
+        If 'path' is ever specified then the search is considered a failure.
+
+        This method is deprecated.  Use find_spec() instead.
+
+        """
+        spec = cls.find_spec(fullname, path)
+        return spec.loader if spec is not None else None
+
+    @classmethod
+    def create_module(self, spec):
+        """Create a built-in module"""
+        if spec.name not in sys.builtin_module_names:
+            raise ImportError('{!r} is not a built-in module'.format(spec.name),
+                              name=spec.name)
+        return _call_with_frames_removed(_imp.create_builtin, spec)
+
+    @classmethod
+    def exec_module(self, module):
+        """Exec a built-in module"""
+        _call_with_frames_removed(_imp.exec_builtin, module)
+
+    @classmethod
+    @_requires_builtin
+    def get_code(cls, fullname):
+        """Return None as built-in modules do not have code objects."""
+        return None
+
+    @classmethod
+    @_requires_builtin
+    def get_source(cls, fullname):
+        """Return None as built-in modules do not have source code."""
+        return None
+
+    @classmethod
+    @_requires_builtin
+    def is_package(cls, fullname):
+        """Return False as built-in modules are never packages."""
+        return False
+
+    load_module = classmethod(_load_module_shim)
+
+
+class FrozenImporter:
+
+    """Meta path import for frozen modules.
+
+    All methods are either class or static methods to avoid the need to
+    instantiate the class.
+
+    """
+
+    _ORIGIN = "frozen"
+
+    @staticmethod
+    def module_repr(m):
+        """Return repr for the module.
+
+        The method is deprecated.  The import machinery does the job itself.
+
+        """
+        return '<module {!r} ({})>'.format(m.__name__, FrozenImporter._ORIGIN)
+
+    @classmethod
+    def find_spec(cls, fullname, path=None, target=None):
+        if _imp.is_frozen(fullname):
+            return spec_from_loader(fullname, cls, origin=cls._ORIGIN)
+        else:
+            return None
+
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        """Find a frozen module.
+
+        This method is deprecated.  Use find_spec() instead.
+
+        """
+        return cls if _imp.is_frozen(fullname) else None
+
+    @classmethod
+    def create_module(cls, spec):
+        """Use default semantics for module creation."""
+
+    @staticmethod
+    def exec_module(module):
+        name = module.__spec__.name
+        if not _imp.is_frozen(name):
+            raise ImportError('{!r} is not a frozen module'.format(name),
+                              name=name)
+        code = _call_with_frames_removed(_imp.get_frozen_object, name)
+        exec(code, module.__dict__)
+
+    @classmethod
+    def load_module(cls, fullname):
+        """Load a frozen module.
+
+        This method is deprecated.  Use exec_module() instead.
+
+        """
+        return _load_module_shim(cls, fullname)
+
+    @classmethod
+    @_requires_frozen
+    def get_code(cls, fullname):
+        """Return the code object for the frozen module."""
+        return _imp.get_frozen_object(fullname)
+
+    @classmethod
+    @_requires_frozen
+    def get_source(cls, fullname):
+        """Return None as frozen modules do not have source code."""
+        return None
+
+    @classmethod
+    @_requires_frozen
+    def is_package(cls, fullname):
+        """Return True if the frozen module is a package."""
+        return _imp.is_frozen_package(fullname)
+
+
+# Import itself ###############################################################
+
+class _ImportLockContext:
+
+    """Context manager for the import lock."""
+
+    def __enter__(self):
+        """Acquire the import lock."""
+        _imp.acquire_lock()
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        """Release the import lock regardless of any raised exceptions."""
+        _imp.release_lock()
+
+
+def _resolve_name(name, package, level):
+    """Resolve a relative module name to an absolute one."""
+    bits = package.rsplit('.', level - 1)
+    if len(bits) < level:
+        raise ValueError('attempted relative import beyond top-level package')
+    base = bits[0]
+    return '{}.{}'.format(base, name) if name else base
+
+
+def _find_spec_legacy(finder, name, path):
+    # This would be a good place for a DeprecationWarning if
+    # we ended up going that route.
+    loader = finder.find_module(name, path)
+    if loader is None:
+        return None
+    return spec_from_loader(name, loader)
+
+
+def _find_spec(name, path, target=None):
+    """Find a module's spec."""
+    meta_path = sys.meta_path
+    if meta_path is None:
+        # PyImport_Cleanup() is running or has been called.
+        raise ImportError("sys.meta_path is None, Python is likely "
+                          "shutting down")
+
+    if not meta_path:
+        _warnings.warn('sys.meta_path is empty', ImportWarning)
+
+    # We check sys.modules here for the reload case.  While a passed-in
+    # target will usually indicate a reload there is no guarantee, whereas
+    # sys.modules provides one.
+    is_reload = name in sys.modules
+    for finder in meta_path:
+        with _ImportLockContext():
+            try:
+                find_spec = finder.find_spec
+            except AttributeError:
+                spec = _find_spec_legacy(finder, name, path)
+                if spec is None:
+                    continue
+            else:
+                spec = find_spec(name, path, target)
+        if spec is not None:
+            # The parent import may have already imported this module.
+            if not is_reload and name in sys.modules:
+                module = sys.modules[name]
+                try:
+                    __spec__ = module.__spec__
+                except AttributeError:
+                    # We use the found spec since that is the one that
+                    # we would have used if the parent module hadn't
+                    # beaten us to the punch.
+                    return spec
+                else:
+                    if __spec__ is None:
+                        return spec
+                    else:
+                        return __spec__
+            else:
+                return spec
+    else:
+        return None
+
+
+def _sanity_check(name, package, level):
+    """Verify arguments are "sane"."""
+    if not isinstance(name, str):
+        raise TypeError('module name must be str, not {}'.format(type(name)))
+    if level < 0:
+        raise ValueError('level must be >= 0')
+    if level > 0:
+        if not isinstance(package, str):
+            raise TypeError('__package__ not set to a string')
+        elif not package:
+            raise ImportError('attempted relative import with no known parent '
+                              'package')
+    if not name and level == 0:
+        raise ValueError('Empty module name')
+
+
+_ERR_MSG_PREFIX = 'No module named '
+_ERR_MSG = _ERR_MSG_PREFIX + '{!r}'
+
+def _find_and_load_unlocked(name, import_):
+    path = None
+    parent = name.rpartition('.')[0]
+    if parent:
+        if parent not in sys.modules:
+            _call_with_frames_removed(import_, parent)
+        # Crazy side-effects!
+        if name in sys.modules:
+            return sys.modules[name]
+        parent_module = sys.modules[parent]
+        try:
+            path = parent_module.__path__
+        except AttributeError:
+            msg = (_ERR_MSG + '; {!r} is not a package').format(name, parent)
+            raise ModuleNotFoundError(msg, name=name) from None
+    spec = _find_spec(name, path)
+    if spec is None:
+        raise ModuleNotFoundError(_ERR_MSG.format(name), name=name)
+    else:
+        module = _load_unlocked(spec)
+    if parent:
+        # Set the module as an attribute on its parent.
+        parent_module = sys.modules[parent]
+        setattr(parent_module, name.rpartition('.')[2], module)
+    return module
+
+
+_NEEDS_LOADING = object()
+
+
+def _find_and_load(name, import_):
+    """Find and load the module."""
+    with _ModuleLockManager(name):
+        module = sys.modules.get(name, _NEEDS_LOADING)
+        if module is _NEEDS_LOADING:
+            return _find_and_load_unlocked(name, import_)
+
+    if module is None:
+        message = ('import of {} halted; '
+                   'None in sys.modules'.format(name))
+        raise ModuleNotFoundError(message, name=name)
+
+    _lock_unlock_module(name)
+    return module
+
+
+def _gcd_import(name, package=None, level=0):
+    """Import and return the module based on its name, the package the call is
+    being made from, and the level adjustment.
+
+    This function represents the greatest common denominator of functionality
+    between import_module and __import__. This includes setting __package__ if
+    the loader did not.
+
+    """
+    _sanity_check(name, package, level)
+    if level > 0:
+        name = _resolve_name(name, package, level)
+    return _find_and_load(name, _gcd_import)
+
+
+def _handle_fromlist(module, fromlist, import_, *, recursive=False):
+    """Figure out what __import__ should return.
+
+    The import_ parameter is a callable which takes the name of module to
+    import. It is required to decouple the function from assuming importlib's
+    import implementation is desired.
+
+    """
+    # The hell that is fromlist ...
+    # If a package was imported, try to import stuff from fromlist.
+    for x in fromlist:
+        if not isinstance(x, str):
+            if recursive:
+                where = module.__name__ + '.__all__'
+            else:
+                where = "``from list''"
+            raise TypeError(f"Item in {where} must be str, "
+                            f"not {type(x).__name__}")
+        elif x == '*':
+            if not recursive and hasattr(module, '__all__'):
+                _handle_fromlist(module, module.__all__, import_,
+                                 recursive=True)
+        elif not hasattr(module, x):
+            from_name = '{}.{}'.format(module.__name__, x)
+            try:
+                _call_with_frames_removed(import_, from_name)
+            except ModuleNotFoundError as exc:
+                # Backwards-compatibility dictates we ignore failed
+                # imports triggered by fromlist for modules that don't
+                # exist.
+                if (exc.name == from_name and
+                    sys.modules.get(from_name, _NEEDS_LOADING) is not None):
+                    continue
+                raise
+    return module
+
+
+def _calc___package__(globals):
+    """Calculate what __package__ should be.
+
+    __package__ is not guaranteed to be defined or could be set to None
+    to represent that its proper value is unknown.
+
+    """
+    package = globals.get('__package__')
+    spec = globals.get('__spec__')
+    if package is not None:
+        if spec is not None and package != spec.parent:
+            _warnings.warn("__package__ != __spec__.parent "
+                           f"({package!r} != {spec.parent!r})",
+                           ImportWarning, stacklevel=3)
+        return package
+    elif spec is not None:
+        return spec.parent
+    else:
+        _warnings.warn("can't resolve package from __spec__ or __package__, "
+                       "falling back on __name__ and __path__",
+                       ImportWarning, stacklevel=3)
+        package = globals['__name__']
+        if '__path__' not in globals:
+            package = package.rpartition('.')[0]
+    return package
+
+
+def __import__(name, globals=None, locals=None, fromlist=(), level=0):
+    """Import a module.
+
+    The 'globals' argument is used to infer where the import is occurring from
+    to handle relative imports. The 'locals' argument is ignored. The
+    'fromlist' argument specifies what should exist as attributes on the module
+    being imported (e.g. ``from module import <fromlist>``).  The 'level'
+    argument represents the package location to import from in a relative
+    import (e.g. ``from ..pkg import mod`` would have a 'level' of 2).
+
+    """
+    if level == 0:
+        module = _gcd_import(name)
+    else:
+        globals_ = globals if globals is not None else {}
+        package = _calc___package__(globals_)
+        module = _gcd_import(name, package, level)
+    if not fromlist:
+        # Return up to the first dot in 'name'. This is complicated by the fact
+        # that 'name' may be relative.
+        if level == 0:
+            return _gcd_import(name.partition('.')[0])
+        elif not name:
+            return module
+        else:
+            # Figure out where to slice the module's name up to the first dot
+            # in 'name'.
+            cut_off = len(name) - len(name.partition('.')[0])
+            # Slice end needs to be positive to alleviate need to special-case
+            # when ``'.' not in name``.
+            return sys.modules[module.__name__[:len(module.__name__)-cut_off]]
+    elif hasattr(module, '__path__'):
+        return _handle_fromlist(module, fromlist, _gcd_import)
+    else:
+        return module
+
+
+def _builtin_from_name(name):
+    spec = BuiltinImporter.find_spec(name)
+    if spec is None:
+        raise ImportError('no built-in module named ' + name)
+    return _load_unlocked(spec)
+
+
+def _setup(sys_module, _imp_module):
+    """Setup importlib by importing needed built-in modules and injecting them
+    into the global namespace.
+
+    As sys is needed for sys.modules access and _imp is needed to load built-in
+    modules, those two modules must be explicitly passed in.
+
+    """
+    global _imp, sys
+    _imp = _imp_module
+    sys = sys_module
+
+    # Set up the spec for existing builtin/frozen modules.
+    module_type = type(sys)
+    for name, module in sys.modules.items():
+        if isinstance(module, module_type):
+            if name in sys.builtin_module_names:
+                loader = BuiltinImporter
+            elif _imp.is_frozen(name):
+                loader = FrozenImporter
+            else:
+                continue
+            spec = _spec_from_module(module, loader)
+            _init_module_attrs(spec, module)
+
+    # Directly load built-in modules needed during bootstrap.
+    self_module = sys.modules[__name__]
+    for builtin_name in ('_thread', '_warnings', '_weakref'):
+        if builtin_name not in sys.modules:
+            builtin_module = _builtin_from_name(builtin_name)
+        else:
+            builtin_module = sys.modules[builtin_name]
+        setattr(self_module, builtin_name, builtin_module)
+
+
+def _install(sys_module, _imp_module):
+    """Install importers for builtin and frozen modules"""
+    _setup(sys_module, _imp_module)
+
+    sys.meta_path.append(BuiltinImporter)
+    sys.meta_path.append(FrozenImporter)
+
+
+def _install_external_importers():
+    """Install importers that require external filesystem access"""
+    global _bootstrap_external
+    import _frozen_importlib_external
+    _bootstrap_external = _frozen_importlib_external
+    _frozen_importlib_external._install(sys.modules[__name__])
diff --git a/common/py3-stdlib/importlib/_bootstrap_external.py b/common/py3-stdlib/importlib/_bootstrap_external.py
new file mode 100644
index 0000000..b8ac482
--- /dev/null
+++ b/common/py3-stdlib/importlib/_bootstrap_external.py
@@ -0,0 +1,1638 @@
+"""Core implementation of path-based import.
+
+This module is NOT meant to be directly imported! It has been designed such
+that it can be bootstrapped into Python as the implementation of import. As
+such it requires the injection of specific modules and attributes in order to
+work. One should use importlib as the public-facing version of this module.
+
+"""
+# IMPORTANT: Whenever making changes to this module, be sure to run a top-level
+# `make regen-importlib` followed by `make` in order to get the frozen version
+# of the module updated. Not doing so will result in the Makefile to fail for
+# all others who don't have a ./python around to freeze the module in the early
+# stages of compilation.
+#
+
+# See importlib._setup() for what is injected into the global namespace.
+
+# When editing this code be aware that code executed at import time CANNOT
+# reference any injected objects! This includes not only global code but also
+# anything specified at the class level.
+
+# Bootstrap-related code ######################################################
+_CASE_INSENSITIVE_PLATFORMS_STR_KEY = 'win',
+_CASE_INSENSITIVE_PLATFORMS_BYTES_KEY = 'cygwin', 'darwin'
+_CASE_INSENSITIVE_PLATFORMS =  (_CASE_INSENSITIVE_PLATFORMS_BYTES_KEY
+                                + _CASE_INSENSITIVE_PLATFORMS_STR_KEY)
+
+
+def _make_relax_case():
+    if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS):
+        if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS_STR_KEY):
+            key = 'PYTHONCASEOK'
+        else:
+            key = b'PYTHONCASEOK'
+
+        def _relax_case():
+            """True if filenames must be checked case-insensitively."""
+            return key in _os.environ
+    else:
+        def _relax_case():
+            """True if filenames must be checked case-insensitively."""
+            return False
+    return _relax_case
+
+
+def _pack_uint32(x):
+    """Convert a 32-bit integer to little-endian."""
+    return (int(x) & 0xFFFFFFFF).to_bytes(4, 'little')
+
+
+def _unpack_uint32(data):
+    """Convert 4 bytes in little-endian to an integer."""
+    assert len(data) == 4
+    return int.from_bytes(data, 'little')
+
+def _unpack_uint16(data):
+    """Convert 2 bytes in little-endian to an integer."""
+    assert len(data) == 2
+    return int.from_bytes(data, 'little')
+
+
+def _path_join(*path_parts):
+    """Replacement for os.path.join()."""
+    return path_sep.join([part.rstrip(path_separators)
+                          for part in path_parts if part])
+
+
+def _path_split(path):
+    """Replacement for os.path.split()."""
+    if len(path_separators) == 1:
+        front, _, tail = path.rpartition(path_sep)
+        return front, tail
+    for x in reversed(path):
+        if x in path_separators:
+            front, tail = path.rsplit(x, maxsplit=1)
+            return front, tail
+    return '', path
+
+
+def _path_stat(path):
+    """Stat the path.
+
+    Made a separate function to make it easier to override in experiments
+    (e.g. cache stat results).
+
+    """
+    return _os.stat(path)
+
+
+def _path_is_mode_type(path, mode):
+    """Test whether the path is the specified mode type."""
+    try:
+        stat_info = _path_stat(path)
+    except OSError:
+        return False
+    return (stat_info.st_mode & 0o170000) == mode
+
+
+def _path_isfile(path):
+    """Replacement for os.path.isfile."""
+    return _path_is_mode_type(path, 0o100000)
+
+
+def _path_isdir(path):
+    """Replacement for os.path.isdir."""
+    if not path:
+        path = _os.getcwd()
+    return _path_is_mode_type(path, 0o040000)
+
+
+def _path_isabs(path):
+    """Replacement for os.path.isabs.
+
+    Considers a Windows drive-relative path (no drive, but starts with slash) to
+    still be "absolute".
+    """
+    return path.startswith(path_separators) or path[1:3] in _pathseps_with_colon
+
+
+def _write_atomic(path, data, mode=0o666):
+    """Best-effort function to write data to a path atomically.
+    Be prepared to handle a FileExistsError if concurrent writing of the
+    temporary file is attempted."""
+    # id() is used to generate a pseudo-random filename.
+    path_tmp = '{}.{}'.format(path, id(path))
+    fd = _os.open(path_tmp,
+                  _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY, mode & 0o666)
+    try:
+        # We first write data to a temporary file, and then use os.replace() to
+        # perform an atomic rename.
+        with _io.FileIO(fd, 'wb') as file:
+            file.write(data)
+        _os.replace(path_tmp, path)
+    except OSError:
+        try:
+            _os.unlink(path_tmp)
+        except OSError:
+            pass
+        raise
+
+
+_code_type = type(_write_atomic.__code__)
+
+
+# Finder/loader utility code ###############################################
+
+# Magic word to reject .pyc files generated by other Python versions.
+# It should change for each incompatible change to the bytecode.
+#
+# The value of CR and LF is incorporated so if you ever read or write
+# a .pyc file in text mode the magic number will be wrong; also, the
+# Apple MPW compiler swaps their values, botching string constants.
+#
+# There were a variety of old schemes for setting the magic number.
+# The current working scheme is to increment the previous value by
+# 10.
+#
+# Starting with the adoption of PEP 3147 in Python 3.2, every bump in magic
+# number also includes a new "magic tag", i.e. a human readable string used
+# to represent the magic number in __pycache__ directories.  When you change
+# the magic number, you must also set a new unique magic tag.  Generally this
+# can be named after the Python major version of the magic number bump, but
+# it can really be anything, as long as it's different than anything else
+# that's come before.  The tags are included in the following table, starting
+# with Python 3.2a0.
+#
+# Known values:
+#  Python 1.5:   20121
+#  Python 1.5.1: 20121
+#     Python 1.5.2: 20121
+#     Python 1.6:   50428
+#     Python 2.0:   50823
+#     Python 2.0.1: 50823
+#     Python 2.1:   60202
+#     Python 2.1.1: 60202
+#     Python 2.1.2: 60202
+#     Python 2.2:   60717
+#     Python 2.3a0: 62011
+#     Python 2.3a0: 62021
+#     Python 2.3a0: 62011 (!)
+#     Python 2.4a0: 62041
+#     Python 2.4a3: 62051
+#     Python 2.4b1: 62061
+#     Python 2.5a0: 62071
+#     Python 2.5a0: 62081 (ast-branch)
+#     Python 2.5a0: 62091 (with)
+#     Python 2.5a0: 62092 (changed WITH_CLEANUP opcode)
+#     Python 2.5b3: 62101 (fix wrong code: for x, in ...)
+#     Python 2.5b3: 62111 (fix wrong code: x += yield)
+#     Python 2.5c1: 62121 (fix wrong lnotab with for loops and
+#                          storing constants that should have been removed)
+#     Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp)
+#     Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode)
+#     Python 2.6a1: 62161 (WITH_CLEANUP optimization)
+#     Python 2.7a0: 62171 (optimize list comprehensions/change LIST_APPEND)
+#     Python 2.7a0: 62181 (optimize conditional branches:
+#                          introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
+#     Python 2.7a0  62191 (introduce SETUP_WITH)
+#     Python 2.7a0  62201 (introduce BUILD_SET)
+#     Python 2.7a0  62211 (introduce MAP_ADD and SET_ADD)
+#     Python 3000:   3000
+#                    3010 (removed UNARY_CONVERT)
+#                    3020 (added BUILD_SET)
+#                    3030 (added keyword-only parameters)
+#                    3040 (added signature annotations)
+#                    3050 (print becomes a function)
+#                    3060 (PEP 3115 metaclass syntax)
+#                    3061 (string literals become unicode)
+#                    3071 (PEP 3109 raise changes)
+#                    3081 (PEP 3137 make __file__ and __name__ unicode)
+#                    3091 (kill str8 interning)
+#                    3101 (merge from 2.6a0, see 62151)
+#                    3103 (__file__ points to source file)
+#     Python 3.0a4: 3111 (WITH_CLEANUP optimization).
+#     Python 3.0b1: 3131 (lexical exception stacking, including POP_EXCEPT
+                          #3021)
+#     Python 3.1a1: 3141 (optimize list, set and dict comprehensions:
+#                         change LIST_APPEND and SET_ADD, add MAP_ADD #2183)
+#     Python 3.1a1: 3151 (optimize conditional branches:
+#                         introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE
+                          #4715)
+#     Python 3.2a1: 3160 (add SETUP_WITH #6101)
+#                   tag: cpython-32
+#     Python 3.2a2: 3170 (add DUP_TOP_TWO, remove DUP_TOPX and ROT_FOUR #9225)
+#                   tag: cpython-32
+#     Python 3.2a3  3180 (add DELETE_DEREF #4617)
+#     Python 3.3a1  3190 (__class__ super closure changed)
+#     Python 3.3a1  3200 (PEP 3155 __qualname__ added #13448)
+#     Python 3.3a1  3210 (added size modulo 2**32 to the pyc header #13645)
+#     Python 3.3a2  3220 (changed PEP 380 implementation #14230)
+#     Python 3.3a4  3230 (revert changes to implicit __class__ closure #14857)
+#     Python 3.4a1  3250 (evaluate positional default arguments before
+#                        keyword-only defaults #16967)
+#     Python 3.4a1  3260 (add LOAD_CLASSDEREF; allow locals of class to override
+#                        free vars #17853)
+#     Python 3.4a1  3270 (various tweaks to the __class__ closure #12370)
+#     Python 3.4a1  3280 (remove implicit class argument)
+#     Python 3.4a4  3290 (changes to __qualname__ computation #19301)
+#     Python 3.4a4  3300 (more changes to __qualname__ computation #19301)
+#     Python 3.4rc2 3310 (alter __qualname__ computation #20625)
+#     Python 3.5a1  3320 (PEP 465: Matrix multiplication operator #21176)
+#     Python 3.5b1  3330 (PEP 448: Additional Unpacking Generalizations #2292)
+#     Python 3.5b2  3340 (fix dictionary display evaluation order #11205)
+#     Python 3.5b3  3350 (add GET_YIELD_FROM_ITER opcode #24400)
+#     Python 3.5.2  3351 (fix BUILD_MAP_UNPACK_WITH_CALL opcode #27286)
+#     Python 3.6a0  3360 (add FORMAT_VALUE opcode #25483)
+#     Python 3.6a1  3361 (lineno delta of code.co_lnotab becomes signed #26107)
+#     Python 3.6a2  3370 (16 bit wordcode #26647)
+#     Python 3.6a2  3371 (add BUILD_CONST_KEY_MAP opcode #27140)
+#     Python 3.6a2  3372 (MAKE_FUNCTION simplification, remove MAKE_CLOSURE
+#                         #27095)
+#     Python 3.6b1  3373 (add BUILD_STRING opcode #27078)
+#     Python 3.6b1  3375 (add SETUP_ANNOTATIONS and STORE_ANNOTATION opcodes
+#                         #27985)
+#     Python 3.6b1  3376 (simplify CALL_FUNCTIONs & BUILD_MAP_UNPACK_WITH_CALL
+                          #27213)
+#     Python 3.6b1  3377 (set __class__ cell from type.__new__ #23722)
+#     Python 3.6b2  3378 (add BUILD_TUPLE_UNPACK_WITH_CALL #28257)
+#     Python 3.6rc1 3379 (more thorough __class__ validation #23722)
+#     Python 3.7a1  3390 (add LOAD_METHOD and CALL_METHOD opcodes #26110)
+#     Python 3.7a2  3391 (update GET_AITER #31709)
+#     Python 3.7a4  3392 (PEP 552: Deterministic pycs #31650)
+#     Python 3.7b1  3393 (remove STORE_ANNOTATION opcode #32550)
+#     Python 3.7b5  3394 (restored docstring as the first stmt in the body;
+#                         this might affected the first line number #32911)
+#     Python 3.8a1  3400 (move frame block handling to compiler #17611)
+#     Python 3.8a1  3401 (add END_ASYNC_FOR #33041)
+#     Python 3.8a1  3410 (PEP570 Python Positional-Only Parameters #36540)
+#     Python 3.8b2  3411 (Reverse evaluation order of key: value in dict
+#                         comprehensions #35224)
+#     Python 3.8b2  3412 (Swap the position of positional args and positional
+#                         only args in ast.arguments #37593)
+#     Python 3.8b4  3413 (Fix "break" and "continue" in "finally" #37830)
+#
+# MAGIC must change whenever the bytecode emitted by the compiler may no
+# longer be understood by older implementations of the eval loop (usually
+# due to the addition of new opcodes).
+#
+# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
+# in PC/launcher.c must also be updated.
+
+MAGIC_NUMBER = (3413).to_bytes(2, 'little') + b'\r\n'
+_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
+
+_PYCACHE = '__pycache__'
+_OPT = 'opt-'
+
+SOURCE_SUFFIXES = ['.py']  # _setup() adds .pyw as needed.
+
+BYTECODE_SUFFIXES = ['.pyc']
+# Deprecated.
+DEBUG_BYTECODE_SUFFIXES = OPTIMIZED_BYTECODE_SUFFIXES = BYTECODE_SUFFIXES
+
+def cache_from_source(path, debug_override=None, *, optimization=None):
+    """Given the path to a .py file, return the path to its .pyc file.
+
+    The .py file does not need to exist; this simply returns the path to the
+    .pyc file calculated as if the .py file were imported.
+
+    The 'optimization' parameter controls the presumed optimization level of
+    the bytecode file. If 'optimization' is not None, the string representation
+    of the argument is taken and verified to be alphanumeric (else ValueError
+    is raised).
+
+    The debug_override parameter is deprecated. If debug_override is not None,
+    a True value is the same as setting 'optimization' to the empty string
+    while a False value is equivalent to setting 'optimization' to '1'.
+
+    If sys.implementation.cache_tag is None then NotImplementedError is raised.
+
+    """
+    if debug_override is not None:
+        _warnings.warn('the debug_override parameter is deprecated; use '
+                       "'optimization' instead", DeprecationWarning)
+        if optimization is not None:
+            message = 'debug_override or optimization must be set to None'
+            raise TypeError(message)
+        optimization = '' if debug_override else 1
+    path = _os.fspath(path)
+    head, tail = _path_split(path)
+    base, sep, rest = tail.rpartition('.')
+    tag = sys.implementation.cache_tag
+    if tag is None:
+        raise NotImplementedError('sys.implementation.cache_tag is None')
+    almost_filename = ''.join([(base if base else rest), sep, tag])
+    if optimization is None:
+        if sys.flags.optimize == 0:
+            optimization = ''
+        else:
+            optimization = sys.flags.optimize
+    optimization = str(optimization)
+    if optimization != '':
+        if not optimization.isalnum():
+            raise ValueError('{!r} is not alphanumeric'.format(optimization))
+        almost_filename = '{}.{}{}'.format(almost_filename, _OPT, optimization)
+    filename = almost_filename + BYTECODE_SUFFIXES[0]
+    if sys.pycache_prefix is not None:
+        # We need an absolute path to the py file to avoid the possibility of
+        # collisions within sys.pycache_prefix, if someone has two different
+        # `foo/bar.py` on their system and they import both of them using the
+        # same sys.pycache_prefix. Let's say sys.pycache_prefix is
+        # `C:\Bytecode`; the idea here is that if we get `Foo\Bar`, we first
+        # make it absolute (`C:\Somewhere\Foo\Bar`), then make it root-relative
+        # (`Somewhere\Foo\Bar`), so we end up placing the bytecode file in an
+        # unambiguous `C:\Bytecode\Somewhere\Foo\Bar\`.
+        if not _path_isabs(head):
+            head = _path_join(_os.getcwd(), head)
+
+        # Strip initial drive from a Windows path. We know we have an absolute
+        # path here, so the second part of the check rules out a POSIX path that
+        # happens to contain a colon at the second character.
+        if head[1] == ':' and head[0] not in path_separators:
+            head = head[2:]
+
+        # Strip initial path separator from `head` to complete the conversion
+        # back to a root-relative path before joining.
+        return _path_join(
+            sys.pycache_prefix,
+            head.lstrip(path_separators),
+            filename,
+        )
+    return _path_join(head, _PYCACHE, filename)
+
+
+def source_from_cache(path):
+    """Given the path to a .pyc. file, return the path to its .py file.
+
+    The .pyc file does not need to exist; this simply returns the path to
+    the .py file calculated to correspond to the .pyc file.  If path does
+    not conform to PEP 3147/488 format, ValueError will be raised. If
+    sys.implementation.cache_tag is None then NotImplementedError is raised.
+
+    """
+    if sys.implementation.cache_tag is None:
+        raise NotImplementedError('sys.implementation.cache_tag is None')
+    path = _os.fspath(path)
+    head, pycache_filename = _path_split(path)
+    found_in_pycache_prefix = False
+    if sys.pycache_prefix is not None:
+        stripped_path = sys.pycache_prefix.rstrip(path_separators)
+        if head.startswith(stripped_path + path_sep):
+            head = head[len(stripped_path):]
+            found_in_pycache_prefix = True
+    if not found_in_pycache_prefix:
+        head, pycache = _path_split(head)
+        if pycache != _PYCACHE:
+            raise ValueError(f'{_PYCACHE} not bottom-level directory in '
+                             f'{path!r}')
+    dot_count = pycache_filename.count('.')
+    if dot_count not in {2, 3}:
+        raise ValueError(f'expected only 2 or 3 dots in {pycache_filename!r}')
+    elif dot_count == 3:
+        optimization = pycache_filename.rsplit('.', 2)[-2]
+        if not optimization.startswith(_OPT):
+            raise ValueError("optimization portion of filename does not start "
+                             f"with {_OPT!r}")
+        opt_level = optimization[len(_OPT):]
+        if not opt_level.isalnum():
+            raise ValueError(f"optimization level {optimization!r} is not an "
+                             "alphanumeric value")
+    base_filename = pycache_filename.partition('.')[0]
+    return _path_join(head, base_filename + SOURCE_SUFFIXES[0])
+
+
+def _get_sourcefile(bytecode_path):
+    """Convert a bytecode file path to a source path (if possible).
+
+    This function exists purely for backwards-compatibility for
+    PyImport_ExecCodeModuleWithFilenames() in the C API.
+
+    """
+    if len(bytecode_path) == 0:
+        return None
+    rest, _, extension = bytecode_path.rpartition('.')
+    if not rest or extension.lower()[-3:-1] != 'py':
+        return bytecode_path
+    try:
+        source_path = source_from_cache(bytecode_path)
+    except (NotImplementedError, ValueError):
+        source_path = bytecode_path[:-1]
+    return source_path if _path_isfile(source_path) else bytecode_path
+
+
+def _get_cached(filename):
+    if filename.endswith(tuple(SOURCE_SUFFIXES)):
+        try:
+            return cache_from_source(filename)
+        except NotImplementedError:
+            pass
+    elif filename.endswith(tuple(BYTECODE_SUFFIXES)):
+        return filename
+    else:
+        return None
+
+
+def _calc_mode(path):
+    """Calculate the mode permissions for a bytecode file."""
+    try:
+        mode = _path_stat(path).st_mode
+    except OSError:
+        mode = 0o666
+    # We always ensure write access so we can update cached files
+    # later even when the source files are read-only on Windows (#6074)
+    mode |= 0o200
+    return mode
+
+
+def _check_name(method):
+    """Decorator to verify that the module being requested matches the one the
+    loader can handle.
+
+    The first argument (self) must define _name which the second argument is
+    compared against. If the comparison fails then ImportError is raised.
+
+    """
+    def _check_name_wrapper(self, name=None, *args, **kwargs):
+        if name is None:
+            name = self.name
+        elif self.name != name:
+            raise ImportError('loader for %s cannot handle %s' %
+                                (self.name, name), name=name)
+        return method(self, name, *args, **kwargs)
+    try:
+        _wrap = _bootstrap._wrap
+    except NameError:
+        # XXX yuck
+        def _wrap(new, old):
+            for replace in ['__module__', '__name__', '__qualname__', '__doc__']:
+                if hasattr(old, replace):
+                    setattr(new, replace, getattr(old, replace))
+            new.__dict__.update(old.__dict__)
+    _wrap(_check_name_wrapper, method)
+    return _check_name_wrapper
+
+
+def _find_module_shim(self, fullname):
+    """Try to find a loader for the specified module by delegating to
+    self.find_loader().
+
+    This method is deprecated in favor of finder.find_spec().
+
+    """
+    # Call find_loader(). If it returns a string (indicating this
+    # is a namespace package portion), generate a warning and
+    # return None.
+    loader, portions = self.find_loader(fullname)
+    if loader is None and len(portions):
+        msg = 'Not importing directory {}: missing __init__'
+        _warnings.warn(msg.format(portions[0]), ImportWarning)
+    return loader
+
+
+def _classify_pyc(data, name, exc_details):
+    """Perform basic validity checking of a pyc header and return the flags field,
+    which determines how the pyc should be further validated against the source.
+
+    *data* is the contents of the pyc file. (Only the first 16 bytes are
+    required, though.)
+
+    *name* is the name of the module being imported. It is used for logging.
+
+    *exc_details* is a dictionary passed to ImportError if it raised for
+    improved debugging.
+
+    ImportError is raised when the magic number is incorrect or when the flags
+    field is invalid. EOFError is raised when the data is found to be truncated.
+
+    """
+    magic = data[:4]
+    if magic != MAGIC_NUMBER:
+        message = f'bad magic number in {name!r}: {magic!r}'
+        _bootstrap._verbose_message('{}', message)
+        raise ImportError(message, **exc_details)
+    if len(data) < 16:
+        message = f'reached EOF while reading pyc header of {name!r}'
+        _bootstrap._verbose_message('{}', message)
+        raise EOFError(message)
+    flags = _unpack_uint32(data[4:8])
+    # Only the first two flags are defined.
+    if flags & ~0b11:
+        message = f'invalid flags {flags!r} in {name!r}'
+        raise ImportError(message, **exc_details)
+    return flags
+
+
+def _validate_timestamp_pyc(data, source_mtime, source_size, name,
+                            exc_details):
+    """Validate a pyc against the source last-modified time.
+
+    *data* is the contents of the pyc file. (Only the first 16 bytes are
+    required.)
+
+    *source_mtime* is the last modified timestamp of the source file.
+
+    *source_size* is None or the size of the source file in bytes.
+
+    *name* is the name of the module being imported. It is used for logging.
+
+    *exc_details* is a dictionary passed to ImportError if it raised for
+    improved debugging.
+
+    An ImportError is raised if the bytecode is stale.
+
+    """
+    if _unpack_uint32(data[8:12]) != (source_mtime & 0xFFFFFFFF):
+        message = f'bytecode is stale for {name!r}'
+        _bootstrap._verbose_message('{}', message)
+        raise ImportError(message, **exc_details)
+    if (source_size is not None and
+        _unpack_uint32(data[12:16]) != (source_size & 0xFFFFFFFF)):
+        raise ImportError(f'bytecode is stale for {name!r}', **exc_details)
+
+
+def _validate_hash_pyc(data, source_hash, name, exc_details):
+    """Validate a hash-based pyc by checking the real source hash against the one in
+    the pyc header.
+
+    *data* is the contents of the pyc file. (Only the first 16 bytes are
+    required.)
+
+    *source_hash* is the importlib.util.source_hash() of the source file.
+
+    *name* is the name of the module being imported. It is used for logging.
+
+    *exc_details* is a dictionary passed to ImportError if it raised for
+    improved debugging.
+
+    An ImportError is raised if the bytecode is stale.
+
+    """
+    if data[8:16] != source_hash:
+        raise ImportError(
+            f'hash in bytecode doesn\'t match hash of source {name!r}',
+            **exc_details,
+        )
+
+
+def _compile_bytecode(data, name=None, bytecode_path=None, source_path=None):
+    """Compile bytecode as found in a pyc."""
+    code = marshal.loads(data)
+    if isinstance(code, _code_type):
+        _bootstrap._verbose_message('code object from {!r}', bytecode_path)
+        if source_path is not None:
+            _imp._fix_co_filename(code, source_path)
+        return code
+    else:
+        raise ImportError('Non-code object in {!r}'.format(bytecode_path),
+                          name=name, path=bytecode_path)
+
+
+def _code_to_timestamp_pyc(code, mtime=0, source_size=0):
+    "Produce the data for a timestamp-based pyc."
+    data = bytearray(MAGIC_NUMBER)
+    data.extend(_pack_uint32(0))
+    data.extend(_pack_uint32(mtime))
+    data.extend(_pack_uint32(source_size))
+    data.extend(marshal.dumps(code))
+    return data
+
+
+def _code_to_hash_pyc(code, source_hash, checked=True):
+    "Produce the data for a hash-based pyc."
+    data = bytearray(MAGIC_NUMBER)
+    flags = 0b1 | checked << 1
+    data.extend(_pack_uint32(flags))
+    assert len(source_hash) == 8
+    data.extend(source_hash)
+    data.extend(marshal.dumps(code))
+    return data
+
+
+def decode_source(source_bytes):
+    """Decode bytes representing source code and return the string.
+
+    Universal newline support is used in the decoding.
+    """
+    import tokenize  # To avoid bootstrap issues.
+    source_bytes_readline = _io.BytesIO(source_bytes).readline
+    encoding = tokenize.detect_encoding(source_bytes_readline)
+    newline_decoder = _io.IncrementalNewlineDecoder(None, True)
+    return newline_decoder.decode(source_bytes.decode(encoding[0]))
+
+
+# Module specifications #######################################################
+
+_POPULATE = object()
+
+
+def spec_from_file_location(name, location=None, *, loader=None,
+                            submodule_search_locations=_POPULATE):
+    """Return a module spec based on a file location.
+
+    To indicate that the module is a package, set
+    submodule_search_locations to a list of directory paths.  An
+    empty list is sufficient, though its not otherwise useful to the
+    import system.
+
+    The loader must take a spec as its only __init__() arg.
+
+    """
+    if location is None:
+        # The caller may simply want a partially populated location-
+        # oriented spec.  So we set the location to a bogus value and
+        # fill in as much as we can.
+        location = '<unknown>'
+        if hasattr(loader, 'get_filename'):
+            # ExecutionLoader
+            try:
+                location = loader.get_filename(name)
+            except ImportError:
+                pass
+    else:
+        location = _os.fspath(location)
+
+    # If the location is on the filesystem, but doesn't actually exist,
+    # we could return None here, indicating that the location is not
+    # valid.  However, we don't have a good way of testing since an
+    # indirect location (e.g. a zip file or URL) will look like a
+    # non-existent file relative to the filesystem.
+
+    spec = _bootstrap.ModuleSpec(name, loader, origin=location)
+    spec._set_fileattr = True
+
+    # Pick a loader if one wasn't provided.
+    if loader is None:
+        for loader_class, suffixes in _get_supported_file_loaders():
+            if location.endswith(tuple(suffixes)):
+                loader = loader_class(name, location)
+                spec.loader = loader
+                break
+        else:
+            return None
+
+    # Set submodule_search_paths appropriately.
+    if submodule_search_locations is _POPULATE:
+        # Check the loader.
+        if hasattr(loader, 'is_package'):
+            try:
+                is_package = loader.is_package(name)
+            except ImportError:
+                pass
+            else:
+                if is_package:
+                    spec.submodule_search_locations = []
+    else:
+        spec.submodule_search_locations = submodule_search_locations
+    if spec.submodule_search_locations == []:
+        if location:
+            dirname = _path_split(location)[0]
+            spec.submodule_search_locations.append(dirname)
+
+    return spec
+
+
+# Loaders #####################################################################
+
+class WindowsRegistryFinder:
+
+    """Meta path finder for modules declared in the Windows registry."""
+
+    REGISTRY_KEY = (
+        'Software\\Python\\PythonCore\\{sys_version}'
+        '\\Modules\\{fullname}')
+    REGISTRY_KEY_DEBUG = (
+        'Software\\Python\\PythonCore\\{sys_version}'
+        '\\Modules\\{fullname}\\Debug')
+    DEBUG_BUILD = False  # Changed in _setup()
+
+    @classmethod
+    def _open_registry(cls, key):
+        try:
+            return _winreg.OpenKey(_winreg.HKEY_CURRENT_USER, key)
+        except OSError:
+            return _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE, key)
+
+    @classmethod
+    def _search_registry(cls, fullname):
+        if cls.DEBUG_BUILD:
+            registry_key = cls.REGISTRY_KEY_DEBUG
+        else:
+            registry_key = cls.REGISTRY_KEY
+        key = registry_key.format(fullname=fullname,
+                                  sys_version='%d.%d' % sys.version_info[:2])
+        try:
+            with cls._open_registry(key) as hkey:
+                filepath = _winreg.QueryValue(hkey, '')
+        except OSError:
+            return None
+        return filepath
+
+    @classmethod
+    def find_spec(cls, fullname, path=None, target=None):
+        filepath = cls._search_registry(fullname)
+        if filepath is None:
+            return None
+        try:
+            _path_stat(filepath)
+        except OSError:
+            return None
+        for loader, suffixes in _get_supported_file_loaders():
+            if filepath.endswith(tuple(suffixes)):
+                spec = _bootstrap.spec_from_loader(fullname,
+                                                   loader(fullname, filepath),
+                                                   origin=filepath)
+                return spec
+
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        """Find module named in the registry.
+
+        This method is deprecated.  Use exec_module() instead.
+
+        """
+        spec = cls.find_spec(fullname, path)
+        if spec is not None:
+            return spec.loader
+        else:
+            return None
+
+
+class _LoaderBasics:
+
+    """Base class of common code needed by both SourceLoader and
+    SourcelessFileLoader."""
+
+    def is_package(self, fullname):
+        """Concrete implementation of InspectLoader.is_package by checking if
+        the path returned by get_filename has a filename of '__init__.py'."""
+        filename = _path_split(self.get_filename(fullname))[1]
+        filename_base = filename.rsplit('.', 1)[0]
+        tail_name = fullname.rpartition('.')[2]
+        return filename_base == '__init__' and tail_name != '__init__'
+
+    def create_module(self, spec):
+        """Use default semantics for module creation."""
+
+    def exec_module(self, module):
+        """Execute the module."""
+        code = self.get_code(module.__name__)
+        if code is None:
+            raise ImportError('cannot load module {!r} when get_code() '
+                              'returns None'.format(module.__name__))
+        _bootstrap._call_with_frames_removed(exec, code, module.__dict__)
+
+    def load_module(self, fullname):
+        """This module is deprecated."""
+        return _bootstrap._load_module_shim(self, fullname)
+
+
+class SourceLoader(_LoaderBasics):
+
+    def path_mtime(self, path):
+        """Optional method that returns the modification time (an int) for the
+        specified path (a str).
+
+        Raises OSError when the path cannot be handled.
+        """
+        raise OSError
+
+    def path_stats(self, path):
+        """Optional method returning a metadata dict for the specified
+        path (a str).
+
+        Possible keys:
+        - 'mtime' (mandatory) is the numeric timestamp of last source
+          code modification;
+        - 'size' (optional) is the size in bytes of the source code.
+
+        Implementing this method allows the loader to read bytecode files.
+        Raises OSError when the path cannot be handled.
+        """
+        return {'mtime': self.path_mtime(path)}
+
+    def _cache_bytecode(self, source_path, cache_path, data):
+        """Optional method which writes data (bytes) to a file path (a str).
+
+        Implementing this method allows for the writing of bytecode files.
+
+        The source path is needed in order to correctly transfer permissions
+        """
+        # For backwards compatibility, we delegate to set_data()
+        return self.set_data(cache_path, data)
+
+    def set_data(self, path, data):
+        """Optional method which writes data (bytes) to a file path (a str).
+
+        Implementing this method allows for the writing of bytecode files.
+        """
+
+
+    def get_source(self, fullname):
+        """Concrete implementation of InspectLoader.get_source."""
+        path = self.get_filename(fullname)
+        try:
+            source_bytes = self.get_data(path)
+        except OSError as exc:
+            raise ImportError('source not available through get_data()',
+                              name=fullname) from exc
+        return decode_source(source_bytes)
+
+    def source_to_code(self, data, path, *, _optimize=-1):
+        """Return the code object compiled from source.
+
+        The 'data' argument can be any object type that compile() supports.
+        """
+        return _bootstrap._call_with_frames_removed(compile, data, path, 'exec',
+                                        dont_inherit=True, optimize=_optimize)
+
+    def get_code(self, fullname):
+        """Concrete implementation of InspectLoader.get_code.
+
+        Reading of bytecode requires path_stats to be implemented. To write
+        bytecode, set_data must also be implemented.
+
+        """
+        source_path = self.get_filename(fullname)
+        source_mtime = None
+        source_bytes = None
+        source_hash = None
+        hash_based = False
+        check_source = True
+        try:
+            bytecode_path = cache_from_source(source_path)
+        except NotImplementedError:
+            bytecode_path = None
+        else:
+            try:
+                st = self.path_stats(source_path)
+            except OSError:
+                pass
+            else:
+                source_mtime = int(st['mtime'])
+                try:
+                    data = self.get_data(bytecode_path)
+                except OSError:
+                    pass
+                else:
+                    exc_details = {
+                        'name': fullname,
+                        'path': bytecode_path,
+                    }
+                    try:
+                        flags = _classify_pyc(data, fullname, exc_details)
+                        bytes_data = memoryview(data)[16:]
+                        hash_based = flags & 0b1 != 0
+                        if hash_based:
+                            check_source = flags & 0b10 != 0
+                            if (_imp.check_hash_based_pycs != 'never' and
+                                (check_source or
+                                 _imp.check_hash_based_pycs == 'always')):
+                                source_bytes = self.get_data(source_path)
+                                source_hash = _imp.source_hash(
+                                    _RAW_MAGIC_NUMBER,
+                                    source_bytes,
+                                )
+                                _validate_hash_pyc(data, source_hash, fullname,
+                                                   exc_details)
+                        else:
+                            _validate_timestamp_pyc(
+                                data,
+                                source_mtime,
+                                st['size'],
+                                fullname,
+                                exc_details,
+                            )
+                    except (ImportError, EOFError):
+                        pass
+                    else:
+                        _bootstrap._verbose_message('{} matches {}', bytecode_path,
+                                                    source_path)
+                        return _compile_bytecode(bytes_data, name=fullname,
+                                                 bytecode_path=bytecode_path,
+                                                 source_path=source_path)
+        if source_bytes is None:
+            source_bytes = self.get_data(source_path)
+        code_object = self.source_to_code(source_bytes, source_path)
+        _bootstrap._verbose_message('code object from {}', source_path)
+        if (not sys.dont_write_bytecode and bytecode_path is not None and
+                source_mtime is not None):
+            if hash_based:
+                if source_hash is None:
+                    source_hash = _imp.source_hash(source_bytes)
+                data = _code_to_hash_pyc(code_object, source_hash, check_source)
+            else:
+                data = _code_to_timestamp_pyc(code_object, source_mtime,
+                                              len(source_bytes))
+            try:
+                self._cache_bytecode(source_path, bytecode_path, data)
+            except NotImplementedError:
+                pass
+        return code_object
+
+
+class FileLoader:
+
+    """Base file loader class which implements the loader protocol methods that
+    require file system usage."""
+
+    def __init__(self, fullname, path):
+        """Cache the module name and the path to the file found by the
+        finder."""
+        self.name = fullname
+        self.path = path
+
+    def __eq__(self, other):
+        return (self.__class__ == other.__class__ and
+                self.__dict__ == other.__dict__)
+
+    def __hash__(self):
+        return hash(self.name) ^ hash(self.path)
+
+    @_check_name
+    def load_module(self, fullname):
+        """Load a module from a file.
+
+        This method is deprecated.  Use exec_module() instead.
+
+        """
+        # The only reason for this method is for the name check.
+        # Issue #14857: Avoid the zero-argument form of super so the implementation
+        # of that form can be updated without breaking the frozen module
+        return super(FileLoader, self).load_module(fullname)
+
+    @_check_name
+    def get_filename(self, fullname):
+        """Return the path to the source file as found by the finder."""
+        return self.path
+
+    def get_data(self, path):
+        """Return the data from path as raw bytes."""
+        if isinstance(self, (SourceLoader, ExtensionFileLoader)):
+            with _io.open_code(str(path)) as file:
+                return file.read()
+        else:
+            with _io.FileIO(path, 'r') as file:
+                return file.read()
+
+    # ResourceReader ABC API.
+
+    @_check_name
+    def get_resource_reader(self, module):
+        if self.is_package(module):
+            return self
+        return None
+
+    def open_resource(self, resource):
+        path = _path_join(_path_split(self.path)[0], resource)
+        return _io.FileIO(path, 'r')
+
+    def resource_path(self, resource):
+        if not self.is_resource(resource):
+            raise FileNotFoundError
+        path = _path_join(_path_split(self.path)[0], resource)
+        return path
+
+    def is_resource(self, name):
+        if path_sep in name:
+            return False
+        path = _path_join(_path_split(self.path)[0], name)
+        return _path_isfile(path)
+
+    def contents(self):
+        return iter(_os.listdir(_path_split(self.path)[0]))
+
+
+class SourceFileLoader(FileLoader, SourceLoader):
+
+    """Concrete implementation of SourceLoader using the file system."""
+
+    def path_stats(self, path):
+        """Return the metadata for the path."""
+        st = _path_stat(path)
+        return {'mtime': st.st_mtime, 'size': st.st_size}
+
+    def _cache_bytecode(self, source_path, bytecode_path, data):
+        # Adapt between the two APIs
+        mode = _calc_mode(source_path)
+        return self.set_data(bytecode_path, data, _mode=mode)
+
+    def set_data(self, path, data, *, _mode=0o666):
+        """Write bytes data to a file."""
+        parent, filename = _path_split(path)
+        path_parts = []
+        # Figure out what directories are missing.
+        while parent and not _path_isdir(parent):
+            parent, part = _path_split(parent)
+            path_parts.append(part)
+        # Create needed directories.
+        for part in reversed(path_parts):
+            parent = _path_join(parent, part)
+            try:
+                _os.mkdir(parent)
+            except FileExistsError:
+                # Probably another Python process already created the dir.
+                continue
+            except OSError as exc:
+                # Could be a permission error, read-only filesystem: just forget
+                # about writing the data.
+                _bootstrap._verbose_message('could not create {!r}: {!r}',
+                                            parent, exc)
+                return
+        try:
+            _write_atomic(path, data, _mode)
+            _bootstrap._verbose_message('created {!r}', path)
+        except OSError as exc:
+            # Same as above: just don't write the bytecode.
+            _bootstrap._verbose_message('could not create {!r}: {!r}', path,
+                                        exc)
+
+
+class SourcelessFileLoader(FileLoader, _LoaderBasics):
+
+    """Loader which handles sourceless file imports."""
+
+    def get_code(self, fullname):
+        path = self.get_filename(fullname)
+        data = self.get_data(path)
+        # Call _classify_pyc to do basic validation of the pyc but ignore the
+        # result. There's no source to check against.
+        exc_details = {
+            'name': fullname,
+            'path': path,
+        }
+        _classify_pyc(data, fullname, exc_details)
+        return _compile_bytecode(
+            memoryview(data)[16:],
+            name=fullname,
+            bytecode_path=path,
+        )
+
+    def get_source(self, fullname):
+        """Return None as there is no source code."""
+        return None
+
+
+# Filled in by _setup().
+EXTENSION_SUFFIXES = []
+
+
+class ExtensionFileLoader(FileLoader, _LoaderBasics):
+
+    """Loader for extension modules.
+
+    The constructor is designed to work with FileFinder.
+
+    """
+
+    def __init__(self, name, path):
+        self.name = name
+        self.path = path
+
+    def __eq__(self, other):
+        return (self.__class__ == other.__class__ and
+                self.__dict__ == other.__dict__)
+
+    def __hash__(self):
+        return hash(self.name) ^ hash(self.path)
+
+    def create_module(self, spec):
+        """Create an unitialized extension module"""
+        module = _bootstrap._call_with_frames_removed(
+            _imp.create_dynamic, spec)
+        _bootstrap._verbose_message('extension module {!r} loaded from {!r}',
+                         spec.name, self.path)
+        return module
+
+    def exec_module(self, module):
+        """Initialize an extension module"""
+        _bootstrap._call_with_frames_removed(_imp.exec_dynamic, module)
+        _bootstrap._verbose_message('extension module {!r} executed from {!r}',
+                         self.name, self.path)
+
+    def is_package(self, fullname):
+        """Return True if the extension module is a package."""
+        file_name = _path_split(self.path)[1]
+        return any(file_name == '__init__' + suffix
+                   for suffix in EXTENSION_SUFFIXES)
+
+    def get_code(self, fullname):
+        """Return None as an extension module cannot create a code object."""
+        return None
+
+    def get_source(self, fullname):
+        """Return None as extension modules have no source code."""
+        return None
+
+    @_check_name
+    def get_filename(self, fullname):
+        """Return the path to the source file as found by the finder."""
+        return self.path
+
+
+class _NamespacePath:
+    """Represents a namespace package's path.  It uses the module name
+    to find its parent module, and from there it looks up the parent's
+    __path__.  When this changes, the module's own path is recomputed,
+    using path_finder.  For top-level modules, the parent module's path
+    is sys.path."""
+
+    def __init__(self, name, path, path_finder):
+        self._name = name
+        self._path = path
+        self._last_parent_path = tuple(self._get_parent_path())
+        self._path_finder = path_finder
+
+    def _find_parent_path_names(self):
+        """Returns a tuple of (parent-module-name, parent-path-attr-name)"""
+        parent, dot, me = self._name.rpartition('.')
+        if dot == '':
+            # This is a top-level module. sys.path contains the parent path.
+            return 'sys', 'path'
+        # Not a top-level module. parent-module.__path__ contains the
+        #  parent path.
+        return parent, '__path__'
+
+    def _get_parent_path(self):
+        parent_module_name, path_attr_name = self._find_parent_path_names()
+        return getattr(sys.modules[parent_module_name], path_attr_name)
+
+    def _recalculate(self):
+        # If the parent's path has changed, recalculate _path
+        parent_path = tuple(self._get_parent_path()) # Make a copy
+        if parent_path != self._last_parent_path:
+            spec = self._path_finder(self._name, parent_path)
+            # Note that no changes are made if a loader is returned, but we
+            #  do remember the new parent path
+            if spec is not None and spec.loader is None:
+                if spec.submodule_search_locations:
+                    self._path = spec.submodule_search_locations
+            self._last_parent_path = parent_path     # Save the copy
+        return self._path
+
+    def __iter__(self):
+        return iter(self._recalculate())
+
+    def __getitem__(self, index):
+        return self._recalculate()[index]
+
+    def __setitem__(self, index, path):
+        self._path[index] = path
+
+    def __len__(self):
+        return len(self._recalculate())
+
+    def __repr__(self):
+        return '_NamespacePath({!r})'.format(self._path)
+
+    def __contains__(self, item):
+        return item in self._recalculate()
+
+    def append(self, item):
+        self._path.append(item)
+
+
+# We use this exclusively in module_from_spec() for backward-compatibility.
+class _NamespaceLoader:
+    def __init__(self, name, path, path_finder):
+        self._path = _NamespacePath(name, path, path_finder)
+
+    @classmethod
+    def module_repr(cls, module):
+        """Return repr for the module.
+
+        The method is deprecated.  The import machinery does the job itself.
+
+        """
+        return '<module {!r} (namespace)>'.format(module.__name__)
+
+    def is_package(self, fullname):
+        return True
+
+    def get_source(self, fullname):
+        return ''
+
+    def get_code(self, fullname):
+        return compile('', '<string>', 'exec', dont_inherit=True)
+
+    def create_module(self, spec):
+        """Use default semantics for module creation."""
+
+    def exec_module(self, module):
+        pass
+
+    def load_module(self, fullname):
+        """Load a namespace module.
+
+        This method is deprecated.  Use exec_module() instead.
+
+        """
+        # The import system never calls this method.
+        _bootstrap._verbose_message('namespace module loaded with path {!r}',
+                                    self._path)
+        return _bootstrap._load_module_shim(self, fullname)
+
+
+# Finders #####################################################################
+
+class PathFinder:
+
+    """Meta path finder for sys.path and package __path__ attributes."""
+
+    @classmethod
+    def invalidate_caches(cls):
+        """Call the invalidate_caches() method on all path entry finders
+        stored in sys.path_importer_caches (where implemented)."""
+        for name, finder in list(sys.path_importer_cache.items()):
+            if finder is None:
+                del sys.path_importer_cache[name]
+            elif hasattr(finder, 'invalidate_caches'):
+                finder.invalidate_caches()
+
+    @classmethod
+    def _path_hooks(cls, path):
+        """Search sys.path_hooks for a finder for 'path'."""
+        if sys.path_hooks is not None and not sys.path_hooks:
+            _warnings.warn('sys.path_hooks is empty', ImportWarning)
+        for hook in sys.path_hooks:
+            try:
+                return hook(path)
+            except ImportError:
+                continue
+        else:
+            return None
+
+    @classmethod
+    def _path_importer_cache(cls, path):
+        """Get the finder for the path entry from sys.path_importer_cache.
+
+        If the path entry is not in the cache, find the appropriate finder
+        and cache it. If no finder is available, store None.
+
+        """
+        if path == '':
+            try:
+                path = _os.getcwd()
+            except FileNotFoundError:
+                # Don't cache the failure as the cwd can easily change to
+                # a valid directory later on.
+                return None
+        try:
+            finder = sys.path_importer_cache[path]
+        except KeyError:
+            finder = cls._path_hooks(path)
+            sys.path_importer_cache[path] = finder
+        return finder
+
+    @classmethod
+    def _legacy_get_spec(cls, fullname, finder):
+        # This would be a good place for a DeprecationWarning if
+        # we ended up going that route.
+        if hasattr(finder, 'find_loader'):
+            loader, portions = finder.find_loader(fullname)
+        else:
+            loader = finder.find_module(fullname)
+            portions = []
+        if loader is not None:
+            return _bootstrap.spec_from_loader(fullname, loader)
+        spec = _bootstrap.ModuleSpec(fullname, None)
+        spec.submodule_search_locations = portions
+        return spec
+
+    @classmethod
+    def _get_spec(cls, fullname, path, target=None):
+        """Find the loader or namespace_path for this module/package name."""
+        # If this ends up being a namespace package, namespace_path is
+        #  the list of paths that will become its __path__
+        namespace_path = []
+        for entry in path:
+            if not isinstance(entry, (str, bytes)):
+                continue
+            finder = cls._path_importer_cache(entry)
+            if finder is not None:
+                if hasattr(finder, 'find_spec'):
+                    spec = finder.find_spec(fullname, target)
+                else:
+                    spec = cls._legacy_get_spec(fullname, finder)
+                if spec is None:
+                    continue
+                if spec.loader is not None:
+                    return spec
+                portions = spec.submodule_search_locations
+                if portions is None:
+                    raise ImportError('spec missing loader')
+                # This is possibly part of a namespace package.
+                #  Remember these path entries (if any) for when we
+                #  create a namespace package, and continue iterating
+                #  on path.
+                namespace_path.extend(portions)
+        else:
+            spec = _bootstrap.ModuleSpec(fullname, None)
+            spec.submodule_search_locations = namespace_path
+            return spec
+
+    @classmethod
+    def find_spec(cls, fullname, path=None, target=None):
+        """Try to find a spec for 'fullname' on sys.path or 'path'.
+
+        The search is based on sys.path_hooks and sys.path_importer_cache.
+        """
+        if path is None:
+            path = sys.path
+        spec = cls._get_spec(fullname, path, target)
+        if spec is None:
+            return None
+        elif spec.loader is None:
+            namespace_path = spec.submodule_search_locations
+            if namespace_path:
+                # We found at least one namespace path.  Return a spec which
+                # can create the namespace package.
+                spec.origin = None
+                spec.submodule_search_locations = _NamespacePath(fullname, namespace_path, cls._get_spec)
+                return spec
+            else:
+                return None
+        else:
+            return spec
+
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        """find the module on sys.path or 'path' based on sys.path_hooks and
+        sys.path_importer_cache.
+
+        This method is deprecated.  Use find_spec() instead.
+
+        """
+        spec = cls.find_spec(fullname, path)
+        if spec is None:
+            return None
+        return spec.loader
+
+    @classmethod
+    def find_distributions(cls, *args, **kwargs):
+        """
+        Find distributions.
+
+        Return an iterable of all Distribution instances capable of
+        loading the metadata for packages matching ``context.name``
+        (or all names if ``None`` indicated) along the paths in the list
+        of directories ``context.path``.
+        """
+        from importlib.metadata import MetadataPathFinder
+        return MetadataPathFinder.find_distributions(*args, **kwargs)
+
+
+class FileFinder:
+
+    """File-based finder.
+
+    Interactions with the file system are cached for performance, being
+    refreshed when the directory the finder is handling has been modified.
+
+    """
+
+    def __init__(self, path, *loader_details):
+        """Initialize with the path to search on and a variable number of
+        2-tuples containing the loader and the file suffixes the loader
+        recognizes."""
+        loaders = []
+        for loader, suffixes in loader_details:
+            loaders.extend((suffix, loader) for suffix in suffixes)
+        self._loaders = loaders
+        # Base (directory) path
+        self.path = path or '.'
+        self._path_mtime = -1
+        self._path_cache = set()
+        self._relaxed_path_cache = set()
+
+    def invalidate_caches(self):
+        """Invalidate the directory mtime."""
+        self._path_mtime = -1
+
+    find_module = _find_module_shim
+
+    def find_loader(self, fullname):
+        """Try to find a loader for the specified module, or the namespace
+        package portions. Returns (loader, list-of-portions).
+
+        This method is deprecated.  Use find_spec() instead.
+
+        """
+        spec = self.find_spec(fullname)
+        if spec is None:
+            return None, []
+        return spec.loader, spec.submodule_search_locations or []
+
+    def _get_spec(self, loader_class, fullname, path, smsl, target):
+        loader = loader_class(fullname, path)
+        return spec_from_file_location(fullname, path, loader=loader,
+                                       submodule_search_locations=smsl)
+
+    def find_spec(self, fullname, target=None):
+        """Try to find a spec for the specified module.
+
+        Returns the matching spec, or None if not found.
+        """
+        is_namespace = False
+        tail_module = fullname.rpartition('.')[2]
+        try:
+            mtime = _path_stat(self.path or _os.getcwd()).st_mtime
+        except OSError:
+            mtime = -1
+        if mtime != self._path_mtime:
+            self._fill_cache()
+            self._path_mtime = mtime
+        # tail_module keeps the original casing, for __file__ and friends
+        if _relax_case():
+            cache = self._relaxed_path_cache
+            cache_module = tail_module.lower()
+        else:
+            cache = self._path_cache
+            cache_module = tail_module
+        # Check if the module is the name of a directory (and thus a package).
+        if cache_module in cache:
+            base_path = _path_join(self.path, tail_module)
+            for suffix, loader_class in self._loaders:
+                init_filename = '__init__' + suffix
+                full_path = _path_join(base_path, init_filename)
+                if _path_isfile(full_path):
+                    return self._get_spec(loader_class, fullname, full_path, [base_path], target)
+            else:
+                # If a namespace package, return the path if we don't
+                #  find a module in the next section.
+                is_namespace = _path_isdir(base_path)
+        # Check for a file w/ a proper suffix exists.
+        for suffix, loader_class in self._loaders:
+            full_path = _path_join(self.path, tail_module + suffix)
+            _bootstrap._verbose_message('trying {}', full_path, verbosity=2)
+            if cache_module + suffix in cache:
+                if _path_isfile(full_path):
+                    return self._get_spec(loader_class, fullname, full_path,
+                                          None, target)
+        if is_namespace:
+            _bootstrap._verbose_message('possible namespace for {}', base_path)
+            spec = _bootstrap.ModuleSpec(fullname, None)
+            spec.submodule_search_locations = [base_path]
+            return spec
+        return None
+
+    def _fill_cache(self):
+        """Fill the cache of potential modules and packages for this directory."""
+        path = self.path
+        try:
+            contents = _os.listdir(path or _os.getcwd())
+        except (FileNotFoundError, PermissionError, NotADirectoryError):
+            # Directory has either been removed, turned into a file, or made
+            # unreadable.
+            contents = []
+        # We store two cached versions, to handle runtime changes of the
+        # PYTHONCASEOK environment variable.
+        if not sys.platform.startswith('win'):
+            self._path_cache = set(contents)
+        else:
+            # Windows users can import modules with case-insensitive file
+            # suffixes (for legacy reasons). Make the suffix lowercase here
+            # so it's done once instead of for every import. This is safe as
+            # the specified suffixes to check against are always specified in a
+            # case-sensitive manner.
+            lower_suffix_contents = set()
+            for item in contents:
+                name, dot, suffix = item.partition('.')
+                if dot:
+                    new_name = '{}.{}'.format(name, suffix.lower())
+                else:
+                    new_name = name
+                lower_suffix_contents.add(new_name)
+            self._path_cache = lower_suffix_contents
+        if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS):
+            self._relaxed_path_cache = {fn.lower() for fn in contents}
+
+    @classmethod
+    def path_hook(cls, *loader_details):
+        """A class method which returns a closure to use on sys.path_hook
+        which will return an instance using the specified loaders and the path
+        called on the closure.
+
+        If the path called on the closure is not a directory, ImportError is
+        raised.
+
+        """
+        def path_hook_for_FileFinder(path):
+            """Path hook for importlib.machinery.FileFinder."""
+            if not _path_isdir(path):
+                raise ImportError('only directories are supported', path=path)
+            return cls(path, *loader_details)
+
+        return path_hook_for_FileFinder
+
+    def __repr__(self):
+        return 'FileFinder({!r})'.format(self.path)
+
+
+# Import setup ###############################################################
+
+def _fix_up_module(ns, name, pathname, cpathname=None):
+    # This function is used by PyImport_ExecCodeModuleObject().
+    loader = ns.get('__loader__')
+    spec = ns.get('__spec__')
+    if not loader:
+        if spec:
+            loader = spec.loader
+        elif pathname == cpathname:
+            loader = SourcelessFileLoader(name, pathname)
+        else:
+            loader = SourceFileLoader(name, pathname)
+    if not spec:
+        spec = spec_from_file_location(name, pathname, loader=loader)
+    try:
+        ns['__spec__'] = spec
+        ns['__loader__'] = loader
+        ns['__file__'] = pathname
+        ns['__cached__'] = cpathname
+    except Exception:
+        # Not important enough to report.
+        pass
+
+
+def _get_supported_file_loaders():
+    """Returns a list of file-based module loaders.
+
+    Each item is a tuple (loader, suffixes).
+    """
+    extensions = ExtensionFileLoader, _imp.extension_suffixes()
+    source = SourceFileLoader, SOURCE_SUFFIXES
+    bytecode = SourcelessFileLoader, BYTECODE_SUFFIXES
+    return [extensions, source, bytecode]
+
+
+def _setup(_bootstrap_module):
+    """Setup the path-based importers for importlib by importing needed
+    built-in modules and injecting them into the global namespace.
+
+    Other components are extracted from the core bootstrap module.
+
+    """
+    global sys, _imp, _bootstrap
+    _bootstrap = _bootstrap_module
+    sys = _bootstrap.sys
+    _imp = _bootstrap._imp
+
+    # Directly load built-in modules needed during bootstrap.
+    self_module = sys.modules[__name__]
+    for builtin_name in ('_io', '_warnings', 'builtins', 'marshal'):
+        if builtin_name not in sys.modules:
+            builtin_module = _bootstrap._builtin_from_name(builtin_name)
+        else:
+            builtin_module = sys.modules[builtin_name]
+        setattr(self_module, builtin_name, builtin_module)
+
+    # Directly load the os module (needed during bootstrap).
+    os_details = ('posix', ['/']), ('nt', ['\\', '/'])
+    for builtin_os, path_separators in os_details:
+        # Assumption made in _path_join()
+        assert all(len(sep) == 1 for sep in path_separators)
+        path_sep = path_separators[0]
+        if builtin_os in sys.modules:
+            os_module = sys.modules[builtin_os]
+            break
+        else:
+            try:
+                os_module = _bootstrap._builtin_from_name(builtin_os)
+                break
+            except ImportError:
+                continue
+    else:
+        raise ImportError('importlib requires posix or nt')
+    setattr(self_module, '_os', os_module)
+    setattr(self_module, 'path_sep', path_sep)
+    setattr(self_module, 'path_separators', ''.join(path_separators))
+    setattr(self_module, '_pathseps_with_colon', {f':{s}' for s in path_separators})
+
+    # Directly load the _thread module (needed during bootstrap).
+    thread_module = _bootstrap._builtin_from_name('_thread')
+    setattr(self_module, '_thread', thread_module)
+
+    # Directly load the _weakref module (needed during bootstrap).
+    weakref_module = _bootstrap._builtin_from_name('_weakref')
+    setattr(self_module, '_weakref', weakref_module)
+
+    # Directly load the winreg module (needed during bootstrap).
+    if builtin_os == 'nt':
+        winreg_module = _bootstrap._builtin_from_name('winreg')
+        setattr(self_module, '_winreg', winreg_module)
+
+    # Constants
+    setattr(self_module, '_relax_case', _make_relax_case())
+    EXTENSION_SUFFIXES.extend(_imp.extension_suffixes())
+    if builtin_os == 'nt':
+        SOURCE_SUFFIXES.append('.pyw')
+        if '_d.pyd' in EXTENSION_SUFFIXES:
+            WindowsRegistryFinder.DEBUG_BUILD = True
+
+
+def _install(_bootstrap_module):
+    """Install the path-based import components."""
+    _setup(_bootstrap_module)
+    supported_loaders = _get_supported_file_loaders()
+    sys.path_hooks.extend([FileFinder.path_hook(*supported_loaders)])
+    sys.meta_path.append(PathFinder)
diff --git a/common/py3-stdlib/importlib/abc.py b/common/py3-stdlib/importlib/abc.py
new file mode 100644
index 0000000..4b2d3de
--- /dev/null
+++ b/common/py3-stdlib/importlib/abc.py
@@ -0,0 +1,388 @@
+"""Abstract base classes related to import."""
+from . import _bootstrap
+from . import _bootstrap_external
+from . import machinery
+try:
+    import _frozen_importlib
+except ImportError as exc:
+    if exc.name != '_frozen_importlib':
+        raise
+    _frozen_importlib = None
+try:
+    import _frozen_importlib_external
+except ImportError as exc:
+    _frozen_importlib_external = _bootstrap_external
+import abc
+import warnings
+
+
+def _register(abstract_cls, *classes):
+    for cls in classes:
+        abstract_cls.register(cls)
+        if _frozen_importlib is not None:
+            try:
+                frozen_cls = getattr(_frozen_importlib, cls.__name__)
+            except AttributeError:
+                frozen_cls = getattr(_frozen_importlib_external, cls.__name__)
+            abstract_cls.register(frozen_cls)
+
+
+class Finder(metaclass=abc.ABCMeta):
+
+    """Legacy abstract base class for import finders.
+
+    It may be subclassed for compatibility with legacy third party
+    reimplementations of the import system.  Otherwise, finder
+    implementations should derive from the more specific MetaPathFinder
+    or PathEntryFinder ABCs.
+
+    Deprecated since Python 3.3
+    """
+
+    @abc.abstractmethod
+    def find_module(self, fullname, path=None):
+        """An abstract method that should find a module.
+        The fullname is a str and the optional path is a str or None.
+        Returns a Loader object or None.
+        """
+
+
+class MetaPathFinder(Finder):
+
+    """Abstract base class for import finders on sys.meta_path."""
+
+    # We don't define find_spec() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def find_module(self, fullname, path):
+        """Return a loader for the module.
+
+        If no module is found, return None.  The fullname is a str and
+        the path is a list of strings or None.
+
+        This method is deprecated since Python 3.4 in favor of
+        finder.find_spec(). If find_spec() exists then backwards-compatible
+        functionality is provided for this method.
+
+        """
+        warnings.warn("MetaPathFinder.find_module() is deprecated since Python "
+                      "3.4 in favor of MetaPathFinder.find_spec() "
+                      "(available since 3.4)",
+                      DeprecationWarning,
+                      stacklevel=2)
+        if not hasattr(self, 'find_spec'):
+            return None
+        found = self.find_spec(fullname, path)
+        return found.loader if found is not None else None
+
+    def invalidate_caches(self):
+        """An optional method for clearing the finder's cache, if any.
+        This method is used by importlib.invalidate_caches().
+        """
+
+_register(MetaPathFinder, machinery.BuiltinImporter, machinery.FrozenImporter,
+          machinery.PathFinder, machinery.WindowsRegistryFinder)
+
+
+class PathEntryFinder(Finder):
+
+    """Abstract base class for path entry finders used by PathFinder."""
+
+    # We don't define find_spec() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def find_loader(self, fullname):
+        """Return (loader, namespace portion) for the path entry.
+
+        The fullname is a str.  The namespace portion is a sequence of
+        path entries contributing to part of a namespace package. The
+        sequence may be empty.  If loader is not None, the portion will
+        be ignored.
+
+        The portion will be discarded if another path entry finder
+        locates the module as a normal module or package.
+
+        This method is deprecated since Python 3.4 in favor of
+        finder.find_spec(). If find_spec() is provided than backwards-compatible
+        functionality is provided.
+        """
+        warnings.warn("PathEntryFinder.find_loader() is deprecated since Python "
+                      "3.4 in favor of PathEntryFinder.find_spec() "
+                      "(available since 3.4)",
+                      DeprecationWarning,
+                      stacklevel=2)
+        if not hasattr(self, 'find_spec'):
+            return None, []
+        found = self.find_spec(fullname)
+        if found is not None:
+            if not found.submodule_search_locations:
+                portions = []
+            else:
+                portions = found.submodule_search_locations
+            return found.loader, portions
+        else:
+            return None, []
+
+    find_module = _bootstrap_external._find_module_shim
+
+    def invalidate_caches(self):
+        """An optional method for clearing the finder's cache, if any.
+        This method is used by PathFinder.invalidate_caches().
+        """
+
+_register(PathEntryFinder, machinery.FileFinder)
+
+
+class Loader(metaclass=abc.ABCMeta):
+
+    """Abstract base class for import loaders."""
+
+    def create_module(self, spec):
+        """Return a module to initialize and into which to load.
+
+        This method should raise ImportError if anything prevents it
+        from creating a new module.  It may return None to indicate
+        that the spec should create the new module.
+        """
+        # By default, defer to default semantics for the new module.
+        return None
+
+    # We don't define exec_module() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def load_module(self, fullname):
+        """Return the loaded module.
+
+        The module must be added to sys.modules and have import-related
+        attributes set properly.  The fullname is a str.
+
+        ImportError is raised on failure.
+
+        This method is deprecated in favor of loader.exec_module(). If
+        exec_module() exists then it is used to provide a backwards-compatible
+        functionality for this method.
+
+        """
+        if not hasattr(self, 'exec_module'):
+            raise ImportError
+        return _bootstrap._load_module_shim(self, fullname)
+
+    def module_repr(self, module):
+        """Return a module's repr.
+
+        Used by the module type when the method does not raise
+        NotImplementedError.
+
+        This method is deprecated.
+
+        """
+        # The exception will cause ModuleType.__repr__ to ignore this method.
+        raise NotImplementedError
+
+
+class ResourceLoader(Loader):
+
+    """Abstract base class for loaders which can return data from their
+    back-end storage.
+
+    This ABC represents one of the optional protocols specified by PEP 302.
+
+    """
+
+    @abc.abstractmethod
+    def get_data(self, path):
+        """Abstract method which when implemented should return the bytes for
+        the specified path.  The path must be a str."""
+        raise OSError
+
+
+class InspectLoader(Loader):
+
+    """Abstract base class for loaders which support inspection about the
+    modules they can load.
+
+    This ABC represents one of the optional protocols specified by PEP 302.
+
+    """
+
+    def is_package(self, fullname):
+        """Optional method which when implemented should return whether the
+        module is a package.  The fullname is a str.  Returns a bool.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    def get_code(self, fullname):
+        """Method which returns the code object for the module.
+
+        The fullname is a str.  Returns a types.CodeType if possible, else
+        returns None if a code object does not make sense
+        (e.g. built-in module). Raises ImportError if the module cannot be
+        found.
+        """
+        source = self.get_source(fullname)
+        if source is None:
+            return None
+        return self.source_to_code(source)
+
+    @abc.abstractmethod
+    def get_source(self, fullname):
+        """Abstract method which should return the source code for the
+        module.  The fullname is a str.  Returns a str.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    @staticmethod
+    def source_to_code(data, path='<string>'):
+        """Compile 'data' into a code object.
+
+        The 'data' argument can be anything that compile() can handle. The'path'
+        argument should be where the data was retrieved (when applicable)."""
+        return compile(data, path, 'exec', dont_inherit=True)
+
+    exec_module = _bootstrap_external._LoaderBasics.exec_module
+    load_module = _bootstrap_external._LoaderBasics.load_module
+
+_register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter)
+
+
+class ExecutionLoader(InspectLoader):
+
+    """Abstract base class for loaders that wish to support the execution of
+    modules as scripts.
+
+    This ABC represents one of the optional protocols specified in PEP 302.
+
+    """
+
+    @abc.abstractmethod
+    def get_filename(self, fullname):
+        """Abstract method which should return the value that __file__ is to be
+        set to.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    def get_code(self, fullname):
+        """Method to return the code object for fullname.
+
+        Should return None if not applicable (e.g. built-in module).
+        Raise ImportError if the module cannot be found.
+        """
+        source = self.get_source(fullname)
+        if source is None:
+            return None
+        try:
+            path = self.get_filename(fullname)
+        except ImportError:
+            return self.source_to_code(source)
+        else:
+            return self.source_to_code(source, path)
+
+_register(ExecutionLoader, machinery.ExtensionFileLoader)
+
+
+class FileLoader(_bootstrap_external.FileLoader, ResourceLoader, ExecutionLoader):
+
+    """Abstract base class partially implementing the ResourceLoader and
+    ExecutionLoader ABCs."""
+
+_register(FileLoader, machinery.SourceFileLoader,
+            machinery.SourcelessFileLoader)
+
+
+class SourceLoader(_bootstrap_external.SourceLoader, ResourceLoader, ExecutionLoader):
+
+    """Abstract base class for loading source code (and optionally any
+    corresponding bytecode).
+
+    To support loading from source code, the abstractmethods inherited from
+    ResourceLoader and ExecutionLoader need to be implemented. To also support
+    loading from bytecode, the optional methods specified directly by this ABC
+    is required.
+
+    Inherited abstractmethods not implemented in this ABC:
+
+        * ResourceLoader.get_data
+        * ExecutionLoader.get_filename
+
+    """
+
+    def path_mtime(self, path):
+        """Return the (int) modification time for the path (str)."""
+        if self.path_stats.__func__ is SourceLoader.path_stats:
+            raise OSError
+        return int(self.path_stats(path)['mtime'])
+
+    def path_stats(self, path):
+        """Return a metadata dict for the source pointed to by the path (str).
+        Possible keys:
+        - 'mtime' (mandatory) is the numeric timestamp of last source
+          code modification;
+        - 'size' (optional) is the size in bytes of the source code.
+        """
+        if self.path_mtime.__func__ is SourceLoader.path_mtime:
+            raise OSError
+        return {'mtime': self.path_mtime(path)}
+
+    def set_data(self, path, data):
+        """Write the bytes to the path (if possible).
+
+        Accepts a str path and data as bytes.
+
+        Any needed intermediary directories are to be created. If for some
+        reason the file cannot be written because of permissions, fail
+        silently.
+        """
+
+_register(SourceLoader, machinery.SourceFileLoader)
+
+
+class ResourceReader(metaclass=abc.ABCMeta):
+
+    """Abstract base class to provide resource-reading support.
+
+    Loaders that support resource reading are expected to implement
+    the ``get_resource_reader(fullname)`` method and have it either return None
+    or an object compatible with this ABC.
+    """
+
+    @abc.abstractmethod
+    def open_resource(self, resource):
+        """Return an opened, file-like object for binary reading.
+
+        The 'resource' argument is expected to represent only a file name
+        and thus not contain any subdirectory components.
+
+        If the resource cannot be found, FileNotFoundError is raised.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def resource_path(self, resource):
+        """Return the file system path to the specified resource.
+
+        The 'resource' argument is expected to represent only a file name
+        and thus not contain any subdirectory components.
+
+        If the resource does not exist on the file system, raise
+        FileNotFoundError.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def is_resource(self, name):
+        """Return True if the named 'name' is consider a resource."""
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def contents(self):
+        """Return an iterable of strings over the contents of the package."""
+        return []
+
+
+_register(ResourceReader, machinery.SourceFileLoader)
diff --git a/common/py3-stdlib/importlib/machinery.py b/common/py3-stdlib/importlib/machinery.py
new file mode 100644
index 0000000..1b2b5c9
--- /dev/null
+++ b/common/py3-stdlib/importlib/machinery.py
@@ -0,0 +1,21 @@
+"""The machinery of importlib: finders, loaders, hooks, etc."""
+
+import _imp
+
+from ._bootstrap import ModuleSpec
+from ._bootstrap import BuiltinImporter
+from ._bootstrap import FrozenImporter
+from ._bootstrap_external import (SOURCE_SUFFIXES, DEBUG_BYTECODE_SUFFIXES,
+                     OPTIMIZED_BYTECODE_SUFFIXES, BYTECODE_SUFFIXES,
+                     EXTENSION_SUFFIXES)
+from ._bootstrap_external import WindowsRegistryFinder
+from ._bootstrap_external import PathFinder
+from ._bootstrap_external import FileFinder
+from ._bootstrap_external import SourceFileLoader
+from ._bootstrap_external import SourcelessFileLoader
+from ._bootstrap_external import ExtensionFileLoader
+
+
+def all_suffixes():
+    """Returns a list of all recognized module suffixes for this process"""
+    return SOURCE_SUFFIXES + BYTECODE_SUFFIXES + EXTENSION_SUFFIXES
diff --git a/common/py3-stdlib/importlib/metadata.py b/common/py3-stdlib/importlib/metadata.py
new file mode 100644
index 0000000..831f593
--- /dev/null
+++ b/common/py3-stdlib/importlib/metadata.py
@@ -0,0 +1,566 @@
+import io
+import os
+import re
+import abc
+import csv
+import sys
+import email
+import pathlib
+import zipfile
+import operator
+import functools
+import itertools
+import posixpath
+import collections
+
+from configparser import ConfigParser
+from contextlib import suppress
+from importlib import import_module
+from importlib.abc import MetaPathFinder
+from itertools import starmap
+
+
+__all__ = [
+    'Distribution',
+    'DistributionFinder',
+    'PackageNotFoundError',
+    'distribution',
+    'distributions',
+    'entry_points',
+    'files',
+    'metadata',
+    'requires',
+    'version',
+    ]
+
+
+class PackageNotFoundError(ModuleNotFoundError):
+    """The package was not found."""
+
+
+class EntryPoint(
+        collections.namedtuple('EntryPointBase', 'name value group')):
+    """An entry point as defined by Python packaging conventions.
+
+    See `the packaging docs on entry points
+    <https://packaging.python.org/specifications/entry-points/>`_
+    for more information.
+    """
+
+    pattern = re.compile(
+        r'(?P<module>[\w.]+)\s*'
+        r'(:\s*(?P<attr>[\w.]+))?\s*'
+        r'(?P<extras>\[.*\])?\s*$'
+        )
+    """
+    A regular expression describing the syntax for an entry point,
+    which might look like:
+
+        - module
+        - package.module
+        - package.module:attribute
+        - package.module:object.attribute
+        - package.module:attr [extra1, extra2]
+
+    Other combinations are possible as well.
+
+    The expression is lenient about whitespace around the ':',
+    following the attr, and following any extras.
+    """
+
+    def load(self):
+        """Load the entry point from its definition. If only a module
+        is indicated by the value, return that module. Otherwise,
+        return the named object.
+        """
+        match = self.pattern.match(self.value)
+        module = import_module(match.group('module'))
+        attrs = filter(None, (match.group('attr') or '').split('.'))
+        return functools.reduce(getattr, attrs, module)
+
+    @property
+    def extras(self):
+        match = self.pattern.match(self.value)
+        return list(re.finditer(r'\w+', match.group('extras') or ''))
+
+    @classmethod
+    def _from_config(cls, config):
+        return [
+            cls(name, value, group)
+            for group in config.sections()
+            for name, value in config.items(group)
+            ]
+
+    @classmethod
+    def _from_text(cls, text):
+        config = ConfigParser(delimiters='=')
+        # case sensitive: https://stackoverflow.com/q/1611799/812183
+        config.optionxform = str
+        try:
+            config.read_string(text)
+        except AttributeError:  # pragma: nocover
+            # Python 2 has no read_string
+            config.readfp(io.StringIO(text))
+        return EntryPoint._from_config(config)
+
+    def __iter__(self):
+        """
+        Supply iter so one may construct dicts of EntryPoints easily.
+        """
+        return iter((self.name, self))
+
+    def __reduce__(self):
+        return (
+            self.__class__,
+            (self.name, self.value, self.group),
+            )
+
+
+class PackagePath(pathlib.PurePosixPath):
+    """A reference to a path in a package"""
+
+    def read_text(self, encoding='utf-8'):
+        with self.locate().open(encoding=encoding) as stream:
+            return stream.read()
+
+    def read_binary(self):
+        with self.locate().open('rb') as stream:
+            return stream.read()
+
+    def locate(self):
+        """Return a path-like object for this path"""
+        return self.dist.locate_file(self)
+
+
+class FileHash:
+    def __init__(self, spec):
+        self.mode, _, self.value = spec.partition('=')
+
+    def __repr__(self):
+        return '<FileHash mode: {} value: {}>'.format(self.mode, self.value)
+
+
+class Distribution:
+    """A Python distribution package."""
+
+    @abc.abstractmethod
+    def read_text(self, filename):
+        """Attempt to load metadata file given by the name.
+
+        :param filename: The name of the file in the distribution info.
+        :return: The text if found, otherwise None.
+        """
+
+    @abc.abstractmethod
+    def locate_file(self, path):
+        """
+        Given a path to a file in this distribution, return a path
+        to it.
+        """
+
+    @classmethod
+    def from_name(cls, name):
+        """Return the Distribution for the given package name.
+
+        :param name: The name of the distribution package to search for.
+        :return: The Distribution instance (or subclass thereof) for the named
+            package, if found.
+        :raises PackageNotFoundError: When the named package's distribution
+            metadata cannot be found.
+        """
+        for resolver in cls._discover_resolvers():
+            dists = resolver(DistributionFinder.Context(name=name))
+            dist = next(dists, None)
+            if dist is not None:
+                return dist
+        else:
+            raise PackageNotFoundError(name)
+
+    @classmethod
+    def discover(cls, **kwargs):
+        """Return an iterable of Distribution objects for all packages.
+
+        Pass a ``context`` or pass keyword arguments for constructing
+        a context.
+
+        :context: A ``DistributionFinder.Context`` object.
+        :return: Iterable of Distribution objects for all packages.
+        """
+        context = kwargs.pop('context', None)
+        if context and kwargs:
+            raise ValueError("cannot accept context and kwargs")
+        context = context or DistributionFinder.Context(**kwargs)
+        return itertools.chain.from_iterable(
+            resolver(context)
+            for resolver in cls._discover_resolvers()
+            )
+
+    @staticmethod
+    def at(path):
+        """Return a Distribution for the indicated metadata path
+
+        :param path: a string or path-like object
+        :return: a concrete Distribution instance for the path
+        """
+        return PathDistribution(pathlib.Path(path))
+
+    @staticmethod
+    def _discover_resolvers():
+        """Search the meta_path for resolvers."""
+        declared = (
+            getattr(finder, 'find_distributions', None)
+            for finder in sys.meta_path
+            )
+        return filter(None, declared)
+
+    @property
+    def metadata(self):
+        """Return the parsed metadata for this Distribution.
+
+        The returned object will have keys that name the various bits of
+        metadata.  See PEP 566 for details.
+        """
+        text = (
+            self.read_text('METADATA')
+            or self.read_text('PKG-INFO')
+            # This last clause is here to support old egg-info files.  Its
+            # effect is to just end up using the PathDistribution's self._path
+            # (which points to the egg-info file) attribute unchanged.
+            or self.read_text('')
+            )
+        return email.message_from_string(text)
+
+    @property
+    def version(self):
+        """Return the 'Version' metadata for the distribution package."""
+        return self.metadata['Version']
+
+    @property
+    def entry_points(self):
+        return EntryPoint._from_text(self.read_text('entry_points.txt'))
+
+    @property
+    def files(self):
+        """Files in this distribution.
+
+        :return: List of PackagePath for this distribution or None
+
+        Result is `None` if the metadata file that enumerates files
+        (i.e. RECORD for dist-info or SOURCES.txt for egg-info) is
+        missing.
+        Result may be empty if the metadata exists but is empty.
+        """
+        file_lines = self._read_files_distinfo() or self._read_files_egginfo()
+
+        def make_file(name, hash=None, size_str=None):
+            result = PackagePath(name)
+            result.hash = FileHash(hash) if hash else None
+            result.size = int(size_str) if size_str else None
+            result.dist = self
+            return result
+
+        return file_lines and list(starmap(make_file, csv.reader(file_lines)))
+
+    def _read_files_distinfo(self):
+        """
+        Read the lines of RECORD
+        """
+        text = self.read_text('RECORD')
+        return text and text.splitlines()
+
+    def _read_files_egginfo(self):
+        """
+        SOURCES.txt might contain literal commas, so wrap each line
+        in quotes.
+        """
+        text = self.read_text('SOURCES.txt')
+        return text and map('"{}"'.format, text.splitlines())
+
+    @property
+    def requires(self):
+        """Generated requirements specified for this Distribution"""
+        reqs = self._read_dist_info_reqs() or self._read_egg_info_reqs()
+        return reqs and list(reqs)
+
+    def _read_dist_info_reqs(self):
+        return self.metadata.get_all('Requires-Dist')
+
+    def _read_egg_info_reqs(self):
+        source = self.read_text('requires.txt')
+        return source and self._deps_from_requires_text(source)
+
+    @classmethod
+    def _deps_from_requires_text(cls, source):
+        section_pairs = cls._read_sections(source.splitlines())
+        sections = {
+            section: list(map(operator.itemgetter('line'), results))
+            for section, results in
+            itertools.groupby(section_pairs, operator.itemgetter('section'))
+            }
+        return cls._convert_egg_info_reqs_to_simple_reqs(sections)
+
+    @staticmethod
+    def _read_sections(lines):
+        section = None
+        for line in filter(None, lines):
+            section_match = re.match(r'\[(.*)\]$', line)
+            if section_match:
+                section = section_match.group(1)
+                continue
+            yield locals()
+
+    @staticmethod
+    def _convert_egg_info_reqs_to_simple_reqs(sections):
+        """
+        Historically, setuptools would solicit and store 'extra'
+        requirements, including those with environment markers,
+        in separate sections. More modern tools expect each
+        dependency to be defined separately, with any relevant
+        extras and environment markers attached directly to that
+        requirement. This method converts the former to the
+        latter. See _test_deps_from_requires_text for an example.
+        """
+        def make_condition(name):
+            return name and 'extra == "{name}"'.format(name=name)
+
+        def parse_condition(section):
+            section = section or ''
+            extra, sep, markers = section.partition(':')
+            if extra and markers:
+                markers = '({markers})'.format(markers=markers)
+            conditions = list(filter(None, [markers, make_condition(extra)]))
+            return '; ' + ' and '.join(conditions) if conditions else ''
+
+        for section, deps in sections.items():
+            for dep in deps:
+                yield dep + parse_condition(section)
+
+
+class DistributionFinder(MetaPathFinder):
+    """
+    A MetaPathFinder capable of discovering installed distributions.
+    """
+
+    class Context:
+        """
+        Keyword arguments presented by the caller to
+        ``distributions()`` or ``Distribution.discover()``
+        to narrow the scope of a search for distributions
+        in all DistributionFinders.
+
+        Each DistributionFinder may expect any parameters
+        and should attempt to honor the canonical
+        parameters defined below when appropriate.
+        """
+
+        name = None
+        """
+        Specific name for which a distribution finder should match.
+        A name of ``None`` matches all distributions.
+        """
+
+        def __init__(self, **kwargs):
+            vars(self).update(kwargs)
+
+        @property
+        def path(self):
+            """
+            The path that a distribution finder should search.
+
+            Typically refers to Python package paths and defaults
+            to ``sys.path``.
+            """
+            return vars(self).get('path', sys.path)
+
+    @abc.abstractmethod
+    def find_distributions(self, context=Context()):
+        """
+        Find distributions.
+
+        Return an iterable of all Distribution instances capable of
+        loading the metadata for packages matching the ``context``,
+        a DistributionFinder.Context instance.
+        """
+
+
+class FastPath:
+    """
+    Micro-optimized class for searching a path for
+    children.
+    """
+
+    def __init__(self, root):
+        self.root = root
+        self.base = os.path.basename(root).lower()
+
+    def joinpath(self, child):
+        return pathlib.Path(self.root, child)
+
+    def children(self):
+        with suppress(Exception):
+            return os.listdir(self.root or '')
+        with suppress(Exception):
+            return self.zip_children()
+        return []
+
+    def zip_children(self):
+        zip_path = zipfile.Path(self.root)
+        names = zip_path.root.namelist()
+        self.joinpath = zip_path.joinpath
+
+        return (
+            posixpath.split(child)[0]
+            for child in names
+            )
+
+    def is_egg(self, search):
+        base = self.base
+        return (
+            base == search.versionless_egg_name
+            or base.startswith(search.prefix)
+            and base.endswith('.egg'))
+
+    def search(self, name):
+        for child in self.children():
+            n_low = child.lower()
+            if (n_low in name.exact_matches
+                    or n_low.startswith(name.prefix)
+                    and n_low.endswith(name.suffixes)
+                    # legacy case:
+                    or self.is_egg(name) and n_low == 'egg-info'):
+                yield self.joinpath(child)
+
+
+class Prepared:
+    """
+    A prepared search for metadata on a possibly-named package.
+    """
+    normalized = ''
+    prefix = ''
+    suffixes = '.dist-info', '.egg-info'
+    exact_matches = [''][:0]
+    versionless_egg_name = ''
+
+    def __init__(self, name):
+        self.name = name
+        if name is None:
+            return
+        self.normalized = name.lower().replace('-', '_')
+        self.prefix = self.normalized + '-'
+        self.exact_matches = [
+            self.normalized + suffix for suffix in self.suffixes]
+        self.versionless_egg_name = self.normalized + '.egg'
+
+
+class MetadataPathFinder(DistributionFinder):
+    @classmethod
+    def find_distributions(cls, context=DistributionFinder.Context()):
+        """
+        Find distributions.
+
+        Return an iterable of all Distribution instances capable of
+        loading the metadata for packages matching ``context.name``
+        (or all names if ``None`` indicated) along the paths in the list
+        of directories ``context.path``.
+        """
+        found = cls._search_paths(context.name, context.path)
+        return map(PathDistribution, found)
+
+    @classmethod
+    def _search_paths(cls, name, paths):
+        """Find metadata directories in paths heuristically."""
+        return itertools.chain.from_iterable(
+            path.search(Prepared(name))
+            for path in map(FastPath, paths)
+            )
+
+
+
+class PathDistribution(Distribution):
+    def __init__(self, path):
+        """Construct a distribution from a path to the metadata directory.
+
+        :param path: A pathlib.Path or similar object supporting
+                     .joinpath(), __div__, .parent, and .read_text().
+        """
+        self._path = path
+
+    def read_text(self, filename):
+        with suppress(FileNotFoundError, IsADirectoryError, KeyError,
+                      NotADirectoryError, PermissionError):
+            return self._path.joinpath(filename).read_text(encoding='utf-8')
+    read_text.__doc__ = Distribution.read_text.__doc__
+
+    def locate_file(self, path):
+        return self._path.parent / path
+
+
+def distribution(distribution_name):
+    """Get the ``Distribution`` instance for the named package.
+
+    :param distribution_name: The name of the distribution package as a string.
+    :return: A ``Distribution`` instance (or subclass thereof).
+    """
+    return Distribution.from_name(distribution_name)
+
+
+def distributions(**kwargs):
+    """Get all ``Distribution`` instances in the current environment.
+
+    :return: An iterable of ``Distribution`` instances.
+    """
+    return Distribution.discover(**kwargs)
+
+
+def metadata(distribution_name):
+    """Get the metadata for the named package.
+
+    :param distribution_name: The name of the distribution package to query.
+    :return: An email.Message containing the parsed metadata.
+    """
+    return Distribution.from_name(distribution_name).metadata
+
+
+def version(distribution_name):
+    """Get the version string for the named package.
+
+    :param distribution_name: The name of the distribution package to query.
+    :return: The version string for the package as defined in the package's
+        "Version" metadata key.
+    """
+    return distribution(distribution_name).version
+
+
+def entry_points():
+    """Return EntryPoint objects for all installed packages.
+
+    :return: EntryPoint objects for all installed packages.
+    """
+    eps = itertools.chain.from_iterable(
+        dist.entry_points for dist in distributions())
+    by_group = operator.attrgetter('group')
+    ordered = sorted(eps, key=by_group)
+    grouped = itertools.groupby(ordered, by_group)
+    return {
+        group: tuple(eps)
+        for group, eps in grouped
+        }
+
+
+def files(distribution_name):
+    """Return a list of files for the named package.
+
+    :param distribution_name: The name of the distribution package to query.
+    :return: List of files composing the distribution.
+    """
+    return distribution(distribution_name).files
+
+
+def requires(distribution_name):
+    """
+    Return a list of requirements for the named package.
+
+    :return: An iterator of requirements, suitable for
+    packaging.requirement.Requirement.
+    """
+    return distribution(distribution_name).requires
diff --git a/common/py3-stdlib/importlib/resources.py b/common/py3-stdlib/importlib/resources.py
new file mode 100644
index 0000000..fc3a1c9
--- /dev/null
+++ b/common/py3-stdlib/importlib/resources.py
@@ -0,0 +1,259 @@
+import os
+import tempfile
+
+from . import abc as resources_abc
+from contextlib import contextmanager, suppress
+from importlib import import_module
+from importlib.abc import ResourceLoader
+from io import BytesIO, TextIOWrapper
+from pathlib import Path
+from types import ModuleType
+from typing import Iterable, Iterator, Optional, Set, Union   # noqa: F401
+from typing import cast
+from typing.io import BinaryIO, TextIO
+from zipimport import ZipImportError
+
+
+__all__ = [
+    'Package',
+    'Resource',
+    'contents',
+    'is_resource',
+    'open_binary',
+    'open_text',
+    'path',
+    'read_binary',
+    'read_text',
+    ]
+
+
+Package = Union[str, ModuleType]
+Resource = Union[str, os.PathLike]
+
+
+def _get_package(package) -> ModuleType:
+    """Take a package name or module object and return the module.
+
+    If a name, the module is imported.  If the passed or imported module
+    object is not a package, raise an exception.
+    """
+    if hasattr(package, '__spec__'):
+        if package.__spec__.submodule_search_locations is None:
+            raise TypeError('{!r} is not a package'.format(
+                package.__spec__.name))
+        else:
+            return package
+    else:
+        module = import_module(package)
+        if module.__spec__.submodule_search_locations is None:
+            raise TypeError('{!r} is not a package'.format(package))
+        else:
+            return module
+
+
+def _normalize_path(path) -> str:
+    """Normalize a path by ensuring it is a string.
+
+    If the resulting string contains path separators, an exception is raised.
+    """
+    parent, file_name = os.path.split(path)
+    if parent:
+        raise ValueError('{!r} must be only a file name'.format(path))
+    else:
+        return file_name
+
+
+def _get_resource_reader(
+        package: ModuleType) -> Optional[resources_abc.ResourceReader]:
+    # Return the package's loader if it's a ResourceReader.  We can't use
+    # a issubclass() check here because apparently abc.'s __subclasscheck__()
+    # hook wants to create a weak reference to the object, but
+    # zipimport.zipimporter does not support weak references, resulting in a
+    # TypeError.  That seems terrible.
+    spec = package.__spec__
+    if hasattr(spec.loader, 'get_resource_reader'):
+        return cast(resources_abc.ResourceReader,
+                    spec.loader.get_resource_reader(spec.name))
+    return None
+
+
+def _check_location(package):
+    if package.__spec__.origin is None or not package.__spec__.has_location:
+        raise FileNotFoundError(f'Package has no location {package!r}')
+
+
+def open_binary(package: Package, resource: Resource) -> BinaryIO:
+    """Return a file-like object opened for binary reading of the resource."""
+    resource = _normalize_path(resource)
+    package = _get_package(package)
+    reader = _get_resource_reader(package)
+    if reader is not None:
+        return reader.open_resource(resource)
+    _check_location(package)
+    absolute_package_path = os.path.abspath(package.__spec__.origin)
+    package_path = os.path.dirname(absolute_package_path)
+    full_path = os.path.join(package_path, resource)
+    try:
+        return open(full_path, mode='rb')
+    except OSError:
+        # Just assume the loader is a resource loader; all the relevant
+        # importlib.machinery loaders are and an AttributeError for
+        # get_data() will make it clear what is needed from the loader.
+        loader = cast(ResourceLoader, package.__spec__.loader)
+        data = None
+        if hasattr(package.__spec__.loader, 'get_data'):
+            with suppress(OSError):
+                data = loader.get_data(full_path)
+        if data is None:
+            package_name = package.__spec__.name
+            message = '{!r} resource not found in {!r}'.format(
+                resource, package_name)
+            raise FileNotFoundError(message)
+        else:
+            return BytesIO(data)
+
+
+def open_text(package: Package,
+              resource: Resource,
+              encoding: str = 'utf-8',
+              errors: str = 'strict') -> TextIO:
+    """Return a file-like object opened for text reading of the resource."""
+    resource = _normalize_path(resource)
+    package = _get_package(package)
+    reader = _get_resource_reader(package)
+    if reader is not None:
+        return TextIOWrapper(reader.open_resource(resource), encoding, errors)
+    _check_location(package)
+    absolute_package_path = os.path.abspath(package.__spec__.origin)
+    package_path = os.path.dirname(absolute_package_path)
+    full_path = os.path.join(package_path, resource)
+    try:
+        return open(full_path, mode='r', encoding=encoding, errors=errors)
+    except OSError:
+        # Just assume the loader is a resource loader; all the relevant
+        # importlib.machinery loaders are and an AttributeError for
+        # get_data() will make it clear what is needed from the loader.
+        loader = cast(ResourceLoader, package.__spec__.loader)
+        data = None
+        if hasattr(package.__spec__.loader, 'get_data'):
+            with suppress(OSError):
+                data = loader.get_data(full_path)
+        if data is None:
+            package_name = package.__spec__.name
+            message = '{!r} resource not found in {!r}'.format(
+                resource, package_name)
+            raise FileNotFoundError(message)
+        else:
+            return TextIOWrapper(BytesIO(data), encoding, errors)
+
+
+def read_binary(package: Package, resource: Resource) -> bytes:
+    """Return the binary contents of the resource."""
+    resource = _normalize_path(resource)
+    package = _get_package(package)
+    with open_binary(package, resource) as fp:
+        return fp.read()
+
+
+def read_text(package: Package,
+              resource: Resource,
+              encoding: str = 'utf-8',
+              errors: str = 'strict') -> str:
+    """Return the decoded string of the resource.
+
+    The decoding-related arguments have the same semantics as those of
+    bytes.decode().
+    """
+    resource = _normalize_path(resource)
+    package = _get_package(package)
+    with open_text(package, resource, encoding, errors) as fp:
+        return fp.read()
+
+
+@contextmanager
+def path(package: Package, resource: Resource) -> Iterator[Path]:
+    """A context manager providing a file path object to the resource.
+
+    If the resource does not already exist on its own on the file system,
+    a temporary file will be created. If the file was created, the file
+    will be deleted upon exiting the context manager (no exception is
+    raised if the file was deleted prior to the context manager
+    exiting).
+    """
+    resource = _normalize_path(resource)
+    package = _get_package(package)
+    reader = _get_resource_reader(package)
+    if reader is not None:
+        try:
+            yield Path(reader.resource_path(resource))
+            return
+        except FileNotFoundError:
+            pass
+    else:
+        _check_location(package)
+    # Fall-through for both the lack of resource_path() *and* if
+    # resource_path() raises FileNotFoundError.
+    package_directory = Path(package.__spec__.origin).parent
+    file_path = package_directory / resource
+    if file_path.exists():
+        yield file_path
+    else:
+        with open_binary(package, resource) as fp:
+            data = fp.read()
+        # Not using tempfile.NamedTemporaryFile as it leads to deeper 'try'
+        # blocks due to the need to close the temporary file to work on
+        # Windows properly.
+        fd, raw_path = tempfile.mkstemp()
+        try:
+            os.write(fd, data)
+            os.close(fd)
+            yield Path(raw_path)
+        finally:
+            try:
+                os.remove(raw_path)
+            except FileNotFoundError:
+                pass
+
+
+def is_resource(package: Package, name: str) -> bool:
+    """True if 'name' is a resource inside 'package'.
+
+    Directories are *not* resources.
+    """
+    package = _get_package(package)
+    _normalize_path(name)
+    reader = _get_resource_reader(package)
+    if reader is not None:
+        return reader.is_resource(name)
+    try:
+        package_contents = set(contents(package))
+    except (NotADirectoryError, FileNotFoundError):
+        return False
+    if name not in package_contents:
+        return False
+    # Just because the given file_name lives as an entry in the package's
+    # contents doesn't necessarily mean it's a resource.  Directories are not
+    # resources, so let's try to find out if it's a directory or not.
+    path = Path(package.__spec__.origin).parent / name
+    return path.is_file()
+
+
+def contents(package: Package) -> Iterable[str]:
+    """Return an iterable of entries in 'package'.
+
+    Note that not all entries are resources.  Specifically, directories are
+    not considered resources.  Use `is_resource()` on each entry returned here
+    to check if it is a resource or not.
+    """
+    package = _get_package(package)
+    reader = _get_resource_reader(package)
+    if reader is not None:
+        return reader.contents()
+    # Is the package a namespace package?  By definition, namespace packages
+    # cannot have resources.  We could use _check_location() and catch the
+    # exception, but that's extra work, so just inline the check.
+    elif package.__spec__.origin is None or not package.__spec__.has_location:
+        return ()
+    else:
+        package_directory = Path(package.__spec__.origin).parent
+        return os.listdir(package_directory)
diff --git a/common/py3-stdlib/importlib/util.py b/common/py3-stdlib/importlib/util.py
new file mode 100644
index 0000000..201e0f4
--- /dev/null
+++ b/common/py3-stdlib/importlib/util.py
@@ -0,0 +1,300 @@
+"""Utility code for constructing importers, etc."""
+from . import abc
+from ._bootstrap import module_from_spec
+from ._bootstrap import _resolve_name
+from ._bootstrap import spec_from_loader
+from ._bootstrap import _find_spec
+from ._bootstrap_external import MAGIC_NUMBER
+from ._bootstrap_external import _RAW_MAGIC_NUMBER
+from ._bootstrap_external import cache_from_source
+from ._bootstrap_external import decode_source
+from ._bootstrap_external import source_from_cache
+from ._bootstrap_external import spec_from_file_location
+
+from contextlib import contextmanager
+import _imp
+import functools
+import sys
+import types
+import warnings
+
+
+def source_hash(source_bytes):
+    "Return the hash of *source_bytes* as used in hash-based pyc files."
+    return _imp.source_hash(_RAW_MAGIC_NUMBER, source_bytes)
+
+
+def resolve_name(name, package):
+    """Resolve a relative module name to an absolute one."""
+    if not name.startswith('.'):
+        return name
+    elif not package:
+        raise ValueError(f'no package specified for {repr(name)} '
+                         '(required for relative module names)')
+    level = 0
+    for character in name:
+        if character != '.':
+            break
+        level += 1
+    return _resolve_name(name[level:], package, level)
+
+
+def _find_spec_from_path(name, path=None):
+    """Return the spec for the specified module.
+
+    First, sys.modules is checked to see if the module was already imported. If
+    so, then sys.modules[name].__spec__ is returned. If that happens to be
+    set to None, then ValueError is raised. If the module is not in
+    sys.modules, then sys.meta_path is searched for a suitable spec with the
+    value of 'path' given to the finders. None is returned if no spec could
+    be found.
+
+    Dotted names do not have their parent packages implicitly imported. You will
+    most likely need to explicitly import all parent packages in the proper
+    order for a submodule to get the correct spec.
+
+    """
+    if name not in sys.modules:
+        return _find_spec(name, path)
+    else:
+        module = sys.modules[name]
+        if module is None:
+            return None
+        try:
+            spec = module.__spec__
+        except AttributeError:
+            raise ValueError('{}.__spec__ is not set'.format(name)) from None
+        else:
+            if spec is None:
+                raise ValueError('{}.__spec__ is None'.format(name))
+            return spec
+
+
+def find_spec(name, package=None):
+    """Return the spec for the specified module.
+
+    First, sys.modules is checked to see if the module was already imported. If
+    so, then sys.modules[name].__spec__ is returned. If that happens to be
+    set to None, then ValueError is raised. If the module is not in
+    sys.modules, then sys.meta_path is searched for a suitable spec with the
+    value of 'path' given to the finders. None is returned if no spec could
+    be found.
+
+    If the name is for submodule (contains a dot), the parent module is
+    automatically imported.
+
+    The name and package arguments work the same as importlib.import_module().
+    In other words, relative module names (with leading dots) work.
+
+    """
+    fullname = resolve_name(name, package) if name.startswith('.') else name
+    if fullname not in sys.modules:
+        parent_name = fullname.rpartition('.')[0]
+        if parent_name:
+            parent = __import__(parent_name, fromlist=['__path__'])
+            try:
+                parent_path = parent.__path__
+            except AttributeError as e:
+                raise ModuleNotFoundError(
+                    f"__path__ attribute not found on {parent_name!r} "
+                    f"while trying to find {fullname!r}", name=fullname) from e
+        else:
+            parent_path = None
+        return _find_spec(fullname, parent_path)
+    else:
+        module = sys.modules[fullname]
+        if module is None:
+            return None
+        try:
+            spec = module.__spec__
+        except AttributeError:
+            raise ValueError('{}.__spec__ is not set'.format(name)) from None
+        else:
+            if spec is None:
+                raise ValueError('{}.__spec__ is None'.format(name))
+            return spec
+
+
+@contextmanager
+def _module_to_load(name):
+    is_reload = name in sys.modules
+
+    module = sys.modules.get(name)
+    if not is_reload:
+        # This must be done before open() is called as the 'io' module
+        # implicitly imports 'locale' and would otherwise trigger an
+        # infinite loop.
+        module = type(sys)(name)
+        # This must be done before putting the module in sys.modules
+        # (otherwise an optimization shortcut in import.c becomes wrong)
+        module.__initializing__ = True
+        sys.modules[name] = module
+    try:
+        yield module
+    except Exception:
+        if not is_reload:
+            try:
+                del sys.modules[name]
+            except KeyError:
+                pass
+    finally:
+        module.__initializing__ = False
+
+
+def set_package(fxn):
+    """Set __package__ on the returned module.
+
+    This function is deprecated.
+
+    """
+    @functools.wraps(fxn)
+    def set_package_wrapper(*args, **kwargs):
+        warnings.warn('The import system now takes care of this automatically.',
+                      DeprecationWarning, stacklevel=2)
+        module = fxn(*args, **kwargs)
+        if getattr(module, '__package__', None) is None:
+            module.__package__ = module.__name__
+            if not hasattr(module, '__path__'):
+                module.__package__ = module.__package__.rpartition('.')[0]
+        return module
+    return set_package_wrapper
+
+
+def set_loader(fxn):
+    """Set __loader__ on the returned module.
+
+    This function is deprecated.
+
+    """
+    @functools.wraps(fxn)
+    def set_loader_wrapper(self, *args, **kwargs):
+        warnings.warn('The import system now takes care of this automatically.',
+                      DeprecationWarning, stacklevel=2)
+        module = fxn(self, *args, **kwargs)
+        if getattr(module, '__loader__', None) is None:
+            module.__loader__ = self
+        return module
+    return set_loader_wrapper
+
+
+def module_for_loader(fxn):
+    """Decorator to handle selecting the proper module for loaders.
+
+    The decorated function is passed the module to use instead of the module
+    name. The module passed in to the function is either from sys.modules if
+    it already exists or is a new module. If the module is new, then __name__
+    is set the first argument to the method, __loader__ is set to self, and
+    __package__ is set accordingly (if self.is_package() is defined) will be set
+    before it is passed to the decorated function (if self.is_package() does
+    not work for the module it will be set post-load).
+
+    If an exception is raised and the decorator created the module it is
+    subsequently removed from sys.modules.
+
+    The decorator assumes that the decorated function takes the module name as
+    the second argument.
+
+    """
+    warnings.warn('The import system now takes care of this automatically.',
+                  DeprecationWarning, stacklevel=2)
+    @functools.wraps(fxn)
+    def module_for_loader_wrapper(self, fullname, *args, **kwargs):
+        with _module_to_load(fullname) as module:
+            module.__loader__ = self
+            try:
+                is_package = self.is_package(fullname)
+            except (ImportError, AttributeError):
+                pass
+            else:
+                if is_package:
+                    module.__package__ = fullname
+                else:
+                    module.__package__ = fullname.rpartition('.')[0]
+            # If __package__ was not set above, __import__() will do it later.
+            return fxn(self, module, *args, **kwargs)
+
+    return module_for_loader_wrapper
+
+
+class _LazyModule(types.ModuleType):
+
+    """A subclass of the module type which triggers loading upon attribute access."""
+
+    def __getattribute__(self, attr):
+        """Trigger the load of the module and return the attribute."""
+        # All module metadata must be garnered from __spec__ in order to avoid
+        # using mutated values.
+        # Stop triggering this method.
+        self.__class__ = types.ModuleType
+        # Get the original name to make sure no object substitution occurred
+        # in sys.modules.
+        original_name = self.__spec__.name
+        # Figure out exactly what attributes were mutated between the creation
+        # of the module and now.
+        attrs_then = self.__spec__.loader_state['__dict__']
+        original_type = self.__spec__.loader_state['__class__']
+        attrs_now = self.__dict__
+        attrs_updated = {}
+        for key, value in attrs_now.items():
+            # Code that set the attribute may have kept a reference to the
+            # assigned object, making identity more important than equality.
+            if key not in attrs_then:
+                attrs_updated[key] = value
+            elif id(attrs_now[key]) != id(attrs_then[key]):
+                attrs_updated[key] = value
+        self.__spec__.loader.exec_module(self)
+        # If exec_module() was used directly there is no guarantee the module
+        # object was put into sys.modules.
+        if original_name in sys.modules:
+            if id(self) != id(sys.modules[original_name]):
+                raise ValueError(f"module object for {original_name!r} "
+                                  "substituted in sys.modules during a lazy "
+                                  "load")
+        # Update after loading since that's what would happen in an eager
+        # loading situation.
+        self.__dict__.update(attrs_updated)
+        return getattr(self, attr)
+
+    def __delattr__(self, attr):
+        """Trigger the load and then perform the deletion."""
+        # To trigger the load and raise an exception if the attribute
+        # doesn't exist.
+        self.__getattribute__(attr)
+        delattr(self, attr)
+
+
+class LazyLoader(abc.Loader):
+
+    """A loader that creates a module which defers loading until attribute access."""
+
+    @staticmethod
+    def __check_eager_loader(loader):
+        if not hasattr(loader, 'exec_module'):
+            raise TypeError('loader must define exec_module()')
+
+    @classmethod
+    def factory(cls, loader):
+        """Construct a callable which returns the eager loader made lazy."""
+        cls.__check_eager_loader(loader)
+        return lambda *args, **kwargs: cls(loader(*args, **kwargs))
+
+    def __init__(self, loader):
+        self.__check_eager_loader(loader)
+        self.loader = loader
+
+    def create_module(self, spec):
+        return self.loader.create_module(spec)
+
+    def exec_module(self, module):
+        """Make the module load lazily."""
+        module.__spec__.loader = self.loader
+        module.__loader__ = self.loader
+        # Don't need to worry about deep-copying as trying to set an attribute
+        # on an object would have triggered the load,
+        # e.g. ``module.__spec__.loader = None`` would trigger a load from
+        # trying to access module.__spec__.
+        loader_state = {}
+        loader_state['__dict__'] = module.__dict__.copy()
+        loader_state['__class__'] = module.__class__
+        module.__spec__.loader_state = loader_state
+        module.__class__ = _LazyModule