Fix a few doc errors, mostly undefined keywords.
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index f866947..c9f742a 100644
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -32,7 +32,7 @@
 
     `Packages specification <http://www.python.org/doc/essays/packages.html>`__
         Original specification of packages. Some semantics have changed since
-        the writing of this document (e.g. redirecting based on :keyword:`None`
+        the writing of this document (e.g. redirecting based on ``None``
         in :data:`sys.modules`).
 
     The :func:`.__import__` function
@@ -109,7 +109,7 @@
         module. If the :term:`finder` is found on :data:`sys.meta_path` and the
         module to be searched for is a subpackage or module then *path* will
         be the value of :attr:`__path__` from the parent package. If a loader
-        cannot be found, :keyword:`None` is returned.
+        cannot be found, ``None`` is returned.
 
 
 .. class:: Loader
@@ -185,14 +185,14 @@
     .. method:: get_code(fullname)
 
         An abstract method to return the :class:`code` object for a module.
-        :keyword:`None` is returned if the module does not have a code object
+        ``None`` is returned if the module does not have a code object
         (e.g. built-in module).  :exc:`ImportError` is raised if loader cannot
         find the requested module.
 
     .. method:: get_source(fullname)
 
         An abstract method to return the source of a module. It is returned as
-        a text string with universal newlines. Returns :keyword:`None` if no
+        a text string with universal newlines. Returns ``None`` if no
         source is available (e.g. a built-in module). Raises :exc:`ImportError`
         if the loader cannot find the module specified.
 
@@ -320,7 +320,7 @@
     .. method:: source_path(fullname)
 
         An abstract method that returns the path to the source code for a
-        module. Should return :keyword:`None` if there is no source code.
+        module. Should return ``None`` if there is no source code.
         Raises :exc:`ImportError` if the loader knows it cannot handle the
         module.
 
@@ -329,7 +329,7 @@
         A concrete implementation of
         :meth:`importlib.abc.ExecutionLoader.get_filename` that
         relies on :meth:`source_path`. If :meth:`source_path` returns
-        :keyword:`None`, then :exc:`ImportError` is raised.
+        ``None``, then :exc:`ImportError` is raised.
 
     .. method:: load_module(fullname)
 
@@ -374,13 +374,13 @@
 
         An abstract method which returns the modification time for the source
         code of the specified module. The modification time should be an
-        integer. If there is no source code, return :keyword:`None`. If the
+        integer. If there is no source code, return ``None``. If the
         module cannot be found then :exc:`ImportError` is raised.
 
     .. method:: bytecode_path(fullname)
 
         An abstract method which returns the path to the bytecode for the
-        specified module, if it exists. It returns :keyword:`None`
+        specified module, if it exists. It returns ``None``
         if no bytecode exists (yet).
         Raises :exc:`ImportError` if the loader knows it cannot handle the
         module.
@@ -398,8 +398,8 @@
     .. method:: write_bytecode(fullname, bytecode)
 
         An abstract method which has the loader write *bytecode* for future
-        use. If the bytecode is written, return :keyword:`True`. Return
-        :keyword:`False` if the bytecode could not be written. This method
+        use. If the bytecode is written, return ``True``. Return
+        ``False`` if the bytecode could not be written. This method
         should not be called if :data:`sys.dont_write_bytecode` is true.
         The *bytecode* argument should be a bytes string or bytes array.
 
@@ -457,7 +457,7 @@
         :data:`sys.path_importer_cache`, then :data:`sys.path_hooks` is
         searched for a finder for the path entry and, if found, is stored in
         :data:`sys.path_importer_cache` along with being queried about the
-        module. If no finder is ever found then :keyword:`None` is returned.
+        module. If no finder is ever found then ``None`` is returned.
 
 
 :mod:`importlib.util` -- Utility code for importers
@@ -506,7 +506,7 @@
 
     A :term:`decorator` for a :term:`loader` to set the :attr:`__package__`
     attribute on the module returned by the loader. If :attr:`__package__` is
-    set and has a value other than :keyword:`None` it will not be changed.
+    set and has a value other than ``None`` it will not be changed.
     Note that the module returned by the loader is what has the attribute
     set on and not the module found in :data:`sys.modules`.