diff --git a/Lib/lib2to3/fixer_base.py b/Lib/lib2to3/fixer_base.py
index adbbe77..1b11faf 100644
--- a/Lib/lib2to3/fixer_base.py
+++ b/Lib/lib2to3/fixer_base.py
@@ -7,12 +7,6 @@
 import logging
 import itertools
 
-# Get a usable 'set' constructor
-try:
-    set
-except NameError:
-    from sets import Set as set
-
 # Local imports
 from .patcomp import PatternCompiler
 from . import pygram
diff --git a/Lib/lib2to3/fixer_util.py b/Lib/lib2to3/fixer_util.py
index 4b5ca34..8a86e51 100644
--- a/Lib/lib2to3/fixer_util.py
+++ b/Lib/lib2to3/fixer_util.py
@@ -153,30 +153,6 @@
             and node.children[0].value == "["
             and node.children[-1].value == "]")
 
-###########################################################
-### Common portability code. This allows fixers to do, eg,
-###  "from .util import set" and forget about it.
-###########################################################
-
-try:
-    any = any
-except NameError:
-    def any(l):
-        for o in l:
-            if o:
-                return True
-        return False
-
-try:
-    set = set
-except NameError:
-    from sets import Set as set
-
-try:
-    reversed = reversed
-except NameError:
-    def reversed(l):
-        return l[::-1]
 
 ###########################################################
 ### Misc
diff --git a/Lib/lib2to3/fixes/fix_dict.py b/Lib/lib2to3/fixes/fix_dict.py
index 485a08c..dec94c5 100644
--- a/Lib/lib2to3/fixes/fix_dict.py
+++ b/Lib/lib2to3/fixes/fix_dict.py
@@ -28,7 +28,7 @@
 from .. import patcomp
 from ..pgen2 import token
 from .. import fixer_base
-from ..fixer_util import Name, Call, LParen, RParen, ArgList, Dot, set
+from ..fixer_util import Name, Call, LParen, RParen, ArgList, Dot
 from .. import fixer_util
 
 
diff --git a/Lib/lib2to3/fixes/fix_except.py b/Lib/lib2to3/fixes/fix_except.py
index 8387913..dc2a5b1 100644
--- a/Lib/lib2to3/fixes/fix_except.py
+++ b/Lib/lib2to3/fixes/fix_except.py
@@ -25,7 +25,7 @@
 from .. import pytree
 from ..pgen2 import token
 from .. import fixer_base
-from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, reversed
+from ..fixer_util import Assign, Attr, Name, is_tuple, is_list
 
 def find_excepts(nodes):
     for i, n in enumerate(nodes):
diff --git a/Lib/lib2to3/fixes/fix_imports.py b/Lib/lib2to3/fixes/fix_imports.py
index 38e868b..e48c4f0 100644
--- a/Lib/lib2to3/fixes/fix_imports.py
+++ b/Lib/lib2to3/fixes/fix_imports.py
@@ -1,9 +1,9 @@
 """Fix incompatible imports and module references."""
-# Author: Collin Winter
+# Authors: Collin Winter, Nick Edds
 
 # Local imports
 from .. import fixer_base
-from ..fixer_util import Name, attr_chain, any, set
+from ..fixer_util import Name, attr_chain
 
 MAPPING = {'StringIO':  'io',
            'cStringIO': 'io',
@@ -61,36 +61,49 @@
 
 
 def build_pattern(mapping=MAPPING):
-    mod_list = ' | '.join(["module='" + key + "'" for key in mapping.keys()])
-    mod_name_list = ' | '.join(["module_name='" + key + "'" for key in mapping.keys()])
-    yield """import_name< 'import' ((%s)
+    mod_list = ' | '.join(["module_name='%s'" % key for key in mapping])
+    bare_names = alternates(mapping.keys())
+
+    yield """name_import=import_name< 'import' ((%s)
                           | dotted_as_names< any* (%s) any* >) >
           """ % (mod_list, mod_list)
     yield """import_from< 'from' (%s) 'import' ['(']
               ( any | import_as_name< any 'as' any > |
                 import_as_names< any* >)  [')'] >
-          """ % mod_name_list
+          """ % mod_list
     yield """import_name< 'import'
                           dotted_as_name< (%s) 'as' any > >
-          """ % mod_name_list
-    # Find usages of module members in code e.g. urllib.foo(bar)
-    yield """power< (%s)
-             trailer<'.' any > any* >
-          """ % mod_name_list
-    yield """bare_name=%s""" % alternates(mapping.keys())
+          """ % mod_list
+
+    # Find usages of module members in code e.g. thread.foo(bar)
+    yield "power< bare_with_attr=(%s) trailer<'.' any > any* >" % bare_names
+
 
 class FixImports(fixer_base.BaseFix):
-    PATTERN = "|".join(build_pattern())
+
     order = "pre" # Pre-order tree traversal
 
+    # This is overridden in fix_imports2.
     mapping = MAPPING
 
-    # Don't match the node if it's within another match
+    def build_pattern(self):
+        return "|".join(build_pattern(self.mapping))
+
+    def compile_pattern(self):
+        # We override this, so MAPPING can be pragmatically altered and the
+        # changes will be reflected in PATTERN.
+        self.PATTERN = self.build_pattern()
+        super(FixImports, self).compile_pattern()
+
+    # Don't match the node if it's within another match.
     def match(self, node):
         match = super(FixImports, self).match
         results = match(node)
         if results:
-            if any([match(obj) for obj in attr_chain(node, "parent")]):
+            # Module usage could be in the trailier of an attribute lookup, so
+            # we might have nested matches when "bare_with_attr" is present.
+            if "bare_with_attr" not in results and \
+                    any([match(obj) for obj in attr_chain(node, "parent")]):
                 return False
             return results
         return False
@@ -100,20 +113,17 @@
         self.replace = {}
 
     def transform(self, node, results):
-        import_mod = results.get("module")
-        mod_name = results.get("module_name")
-        bare_name = results.get("bare_name")
-
-        if import_mod or mod_name:
-            new_name = self.mapping[(import_mod or mod_name).value]
-
+        import_mod = results.get("module_name")
         if import_mod:
-            self.replace[import_mod.value] = new_name
+            new_name = self.mapping[(import_mod or mod_name).value]
+            if "name_import" in results:
+                # If it's not a "from x import x, y" or "import x as y" import,
+                # marked its usage to be replaced.
+                self.replace[import_mod.value] = new_name
             import_mod.replace(Name(new_name, prefix=import_mod.get_prefix()))
-        elif mod_name:
-            mod_name.replace(Name(new_name, prefix=mod_name.get_prefix()))
-        elif bare_name:
-            bare_name = bare_name[0]
+        else:
+            # Replace usage of the module.
+            bare_name = results["bare_with_attr"][0]
             new_name = self.replace.get(bare_name.value)
             if new_name:
                 bare_name.replace(Name(new_name, prefix=bare_name.get_prefix()))
diff --git a/Lib/lib2to3/fixes/fix_imports2.py b/Lib/lib2to3/fixes/fix_imports2.py
index e82f7e4..bcd7aa6 100644
--- a/Lib/lib2to3/fixes/fix_imports2.py
+++ b/Lib/lib2to3/fixes/fix_imports2.py
@@ -10,7 +10,6 @@
 
 
 class FixImports2(fix_imports.FixImports):
-    PATTERN = "|".join((fix_imports.build_pattern(MAPPING)))
 
     order = "post"
 
diff --git a/Lib/lib2to3/fixes/fix_next.py b/Lib/lib2to3/fixes/fix_next.py
index 9f1861e..492b515 100644
--- a/Lib/lib2to3/fixes/fix_next.py
+++ b/Lib/lib2to3/fixes/fix_next.py
@@ -9,7 +9,7 @@
 from ..pgen2 import token
 from ..pygram import python_symbols as syms
 from .. import fixer_base
-from ..fixer_util import Name, Call, find_binding, any
+from ..fixer_util import Name, Call, find_binding
 
 bind_warning = "Calls to builtin next() possibly shadowed by global binding"
 
diff --git a/Lib/lib2to3/fixes/fix_numliterals.py b/Lib/lib2to3/fixes/fix_numliterals.py
index 682aac5..d821e39 100644
--- a/Lib/lib2to3/fixes/fix_numliterals.py
+++ b/Lib/lib2to3/fixes/fix_numliterals.py
@@ -6,7 +6,7 @@
 # Local imports
 from ..pgen2 import token
 from .. import fixer_base
-from ..fixer_util import Number, set
+from ..fixer_util import Number
 
 
 class FixNumliterals(fixer_base.BaseFix):
diff --git a/Lib/lib2to3/fixes/fix_renames.py b/Lib/lib2to3/fixes/fix_renames.py
index 181c625..3049610 100644
--- a/Lib/lib2to3/fixes/fix_renames.py
+++ b/Lib/lib2to3/fixes/fix_renames.py
@@ -8,7 +8,7 @@
 
 # Local imports
 from .. import fixer_base
-from ..fixer_util import Name, attr_chain, any, set
+from ..fixer_util import Name, attr_chain
 
 MAPPING = {"sys":  {"maxint" : "maxsize"},
           }
diff --git a/Lib/lib2to3/fixes/fix_urllib.py b/Lib/lib2to3/fixes/fix_urllib.py
index 78bf7ab..ea7e9ca 100644
--- a/Lib/lib2to3/fixes/fix_urllib.py
+++ b/Lib/lib2to3/fixes/fix_urllib.py
@@ -7,7 +7,7 @@
 # Local imports
 from .fix_imports import alternates, FixImports
 from .. import fixer_base
-from ..fixer_util import Name, Comma, FromImport, Newline, attr_chain, any, set
+from ..fixer_util import Name, Comma, FromImport, Newline, attr_chain
 
 MAPPING = {'urllib':  [
                 ('urllib.request',
@@ -65,7 +65,9 @@
 
 
 class FixUrllib(FixImports):
-    PATTERN = "|".join(build_pattern())
+
+    def build_pattern(self):
+        return "|".join(build_pattern())
 
     def transform_import(self, node, results):
         """Transform for the basic import case. Replaces the old
diff --git a/Lib/lib2to3/pgen2/parse.py b/Lib/lib2to3/pgen2/parse.py
index 9b1ac2a..6bebdbb 100644
--- a/Lib/lib2to3/pgen2/parse.py
+++ b/Lib/lib2to3/pgen2/parse.py
@@ -10,12 +10,6 @@
 
 """
 
-# Get a usable 'set' constructor
-try:
-    set
-except NameError:
-    from sets import Set as set
-
 # Local imports
 from . import token
 
diff --git a/Lib/lib2to3/pytree.py b/Lib/lib2to3/pytree.py
index c6655a0..ec87a9d 100644
--- a/Lib/lib2to3/pytree.py
+++ b/Lib/lib2to3/pytree.py
@@ -11,6 +11,9 @@
 
 __author__ = "Guido van Rossum <guido@python.org>"
 
+import sys
+from io import StringIO
+
 
 HUGE = 0x7FFFFFFF  # maximum repeat count, default max
 
@@ -655,6 +658,11 @@
         elif self.name == "bare_name":
             yield self._bare_name_matches(nodes)
         else:
+            # The reason for this is that hitting the recursion limit usually
+            # results in some ugly messages about how RuntimeErrors are being
+            # ignored.
+            save_stderr = sys.stderr
+            sys.stderr = StringIO()
             try:
                 for count, r in self._recursive_matches(nodes, 0):
                     if self.name:
@@ -667,6 +675,8 @@
                     if self.name:
                         r[self.name] = nodes[:count]
                     yield count, r
+            finally:
+                sys.stderr = save_stderr
 
     def _iterative_matches(self, nodes):
         """Helper to iteratively yield the matches."""
diff --git a/Lib/lib2to3/refactor.py b/Lib/lib2to3/refactor.py
index 87b0c59..013bca8e 100755
--- a/Lib/lib2to3/refactor.py
+++ b/Lib/lib2to3/refactor.py
@@ -123,8 +123,8 @@
                                     logger=self.logger)
         self.pre_order, self.post_order = self.get_fixers()
 
-        self.pre_order = get_headnode_dict(self.pre_order)
-        self.post_order = get_headnode_dict(self.post_order)
+        self.pre_order_mapping = get_headnode_dict(self.pre_order)
+        self.post_order_mapping = get_headnode_dict(self.post_order)
 
         self.files = []  # List of files that were or should be modified
 
@@ -290,13 +290,12 @@
         # Two calls to chain are required because pre_order.values()
         #   will be a list of lists of fixers:
         #   [[<fixer ...>, <fixer ...>], [<fixer ...>]]
-        all_fixers = chain(chain(*self.pre_order.values()),\
-                           chain(*self.post_order.values()))
+        all_fixers = chain(self.pre_order, self.post_order)
         for fixer in all_fixers:
             fixer.start_tree(tree, name)
 
-        self.traverse_by(self.pre_order, tree.pre_order())
-        self.traverse_by(self.post_order, tree.post_order())
+        self.traverse_by(self.pre_order_mapping, tree.pre_order())
+        self.traverse_by(self.post_order_mapping, tree.post_order())
 
         for fixer in all_fixers:
             fixer.finish_tree(tree, name)
diff --git a/Lib/lib2to3/tests/test_fixers.py b/Lib/lib2to3/tests/test_fixers.py
index 51c019f..7dd1c28 100755
--- a/Lib/lib2to3/tests/test_fixers.py
+++ b/Lib/lib2to3/tests/test_fixers.py
@@ -15,10 +15,7 @@
 from operator import itemgetter
 
 # Local imports
-from .. import pygram
-from .. import pytree
-from .. import refactor
-from .. import fixer_util
+from lib2to3 import pygram, pytree, refactor, fixer_util
 
 
 class FixerTestCase(support.TestCase):
@@ -30,10 +27,9 @@
         self.fixer_log = []
         self.filename = "<string>"
 
-        for order in (self.refactor.pre_order.values(),\
-                      self.refactor.post_order.values()):
-            for fixer in chain(*order):
-                fixer.log = self.fixer_log
+        for fixer in chain(self.refactor.pre_order,
+                           self.refactor.post_order):
+            fixer.log = self.fixer_log
 
     def _check(self, before, after):
         before = support.reformat(before)
@@ -1488,6 +1484,44 @@
                 """ % (new, new)
             self.check(b, a)
 
+            b = """
+                from %s import x
+                %s = 23
+                """ % (old, old)
+            a = """
+                from %s import x
+                %s = 23
+                """ % (new, old)
+            self.check(b, a)
+
+            s = """
+                def f():
+                    %s.method()
+                """ % (old,)
+            self.unchanged(s)
+
+            # test nested usage
+            b = """
+                import %s
+                %s.bar(%s.foo)
+                """ % (old, old, old)
+            a = """
+                import %s
+                %s.bar(%s.foo)
+                """ % (new, new, new)
+            self.check(b, a)
+
+            b = """
+                import %s
+                x.%s
+                """ % (old, old)
+            a = """
+                import %s
+                x.%s
+                """ % (new, old)
+            self.check(b, a)
+
+
 
 class Test_imports2(Test_imports):
     fixer = "imports2"
diff --git a/Lib/lib2to3/tests/test_refactor.py b/Lib/lib2to3/tests/test_refactor.py
index 0814ad7..5a49f01 100644
--- a/Lib/lib2to3/tests/test_refactor.py
+++ b/Lib/lib2to3/tests/test_refactor.py
@@ -161,7 +161,7 @@
         self.assertEqual(len(rt.post_order), 0)
 
         rt = self.rt(explicit=["myfixes.fix_explicit"])
-        for fix in rt.post_order[None]:
+        for fix in rt.post_order:
             if isinstance(fix, FixExplicit):
                 break
         else: