diff -r cf5b910ac4c8 Lib/_compat_pickle.py
--- a/Lib/_compat_pickle.py	Sat Nov 15 10:58:58 2014 -0800
+++ b/Lib/_compat_pickle.py	Sun Nov 16 22:46:48 2014 +0200
@@ -6,8 +6,6 @@
 # lib2to3 and use the mapping defined there, because lib2to3 uses pickle.
 # Thus, this could cause the module to be imported recursively.
 IMPORT_MAPPING = {
-    'StringIO':  'io',
-    'cStringIO': 'io',
     'cPickle': 'pickle',
     '__builtin__' : 'builtins',
     'copy_reg': 'copyreg',
@@ -15,9 +13,7 @@ IMPORT_MAPPING = {
     'SocketServer': 'socketserver',
     'ConfigParser': 'configparser',
     'repr': 'reprlib',
-    'FileDialog': 'tkinter.filedialog',
     'tkFileDialog': 'tkinter.filedialog',
-    'SimpleDialog': 'tkinter.simpledialog',
     'tkSimpleDialog': 'tkinter.simpledialog',
     'tkColorChooser': 'tkinter.colorchooser',
     'tkCommonDialog': 'tkinter.commondialog',
@@ -39,7 +35,6 @@ IMPORT_MAPPING = {
     'dbm': 'dbm.ndbm',
     'gdbm': 'dbm.gnu',
     'xmlrpclib': 'xmlrpc.client',
-    'DocXMLRPCServer': 'xmlrpc.server',
     'SimpleXMLRPCServer': 'xmlrpc.server',
     'httplib': 'http.client',
     'htmlentitydefs' : 'html.entities',
@@ -47,16 +42,10 @@ IMPORT_MAPPING = {
     'Cookie': 'http.cookies',
     'cookielib': 'http.cookiejar',
     'BaseHTTPServer': 'http.server',
-    'SimpleHTTPServer': 'http.server',
-    'CGIHTTPServer': 'http.server',
     'test.test_support': 'test.support',
     'commands': 'subprocess',
-    'UserString' : 'collections',
-    'UserList' : 'collections',
     'urlparse' : 'urllib.parse',
     'robotparser' : 'urllib.robotparser',
-    'whichdb': 'dbm',
-    'anydbm': 'dbm'
 }
 
 
@@ -74,6 +63,7 @@ NAME_MAPPING = {
     ('itertools', 'imap'):         ('builtins', 'map'),
     ('itertools', 'ifilter'):      ('builtins', 'filter'),
     ('itertools', 'ifilterfalse'): ('itertools', 'filterfalse'),
+    ('UserDict', 'IterableUserDict'): ('collections', 'UserDict'),
 }
 
 PYTHON2_EXCEPTIONS = (
@@ -130,8 +120,51 @@ PYTHON2_EXCEPTIONS = (
 for excname in PYTHON2_EXCEPTIONS:
     NAME_MAPPING[("exceptions", excname)] = ("builtins", excname)
 
-NAME_MAPPING[("exceptions", "StandardError")] = ("builtins", "Exception")
-
 # Same, but for 3.x to 2.x
 REVERSE_IMPORT_MAPPING = dict((v, k) for (k, v) in IMPORT_MAPPING.items())
+assert len(REVERSE_IMPORT_MAPPING) == len(IMPORT_MAPPING)
 REVERSE_NAME_MAPPING = dict((v, k) for (k, v) in NAME_MAPPING.items())
+assert len(REVERSE_NAME_MAPPING) == len(NAME_MAPPING)
+
+# Non-mutual mappings.
+
+IMPORT_MAPPING.update({
+    'FileDialog': 'tkinter.filedialog',
+    'SimpleDialog': 'tkinter.simpledialog',
+    'DocXMLRPCServer': 'xmlrpc.server',
+    'SimpleHTTPServer': 'http.server',
+    'CGIHTTPServer': 'http.server',
+    'UserDict' : 'collections',
+    'UserList' : 'collections',
+    'UserString' : 'collections',
+    'whichdb': 'dbm',
+    'anydbm': 'dbm',
+})
+
+NAME_MAPPING.update({
+    ('exceptions', 'StandardError'): ('builtins', 'Exception'),
+})
+
+REVERSE_NAME_MAPPING.update({
+    ('tkinter.filedialog', 'FileDialog'): ('FileDialog', 'FileDialog'),
+    ('tkinter.filedialog', 'LoadFileDialog'): ('FileDialog', 'LoadFileDialog'),
+    ('tkinter.filedialog', 'SaveFileDialog'): ('FileDialog', 'SaveFileDialog'),
+    ('tkinter.simpledialog', 'SimpleDialog'): ('SimpleDialog', 'SimpleDialog'),
+    ('xmlrpc.server', 'ServerHTMLDoc'): ('DocXMLRPCServer', 'ServerHTMLDoc'),
+    ('xmlrpc.server', 'XMLRPCDocGenerator'):
+        ('DocXMLRPCServer', 'XMLRPCDocGenerator'),
+    ('xmlrpc.server', 'DocXMLRPCRequestHandler'):
+        ('DocXMLRPCServer', 'DocXMLRPCRequestHandler'),
+    ('xmlrpc.server', 'DocXMLRPCServer'):
+        ('DocXMLRPCServer', 'DocXMLRPCServer'),
+    ('xmlrpc.server', 'DocCGIXMLRPCRequestHandler'):
+        ('DocXMLRPCServer', 'DocCGIXMLRPCRequestHandler'),
+    ('http.server', 'SimpleHTTPRequestHandler'):
+        ('SimpleHTTPServer', 'SimpleHTTPRequestHandler'),
+    ('http.server', 'CGIHTTPRequestHandler'):
+        ('CGIHTTPServer', 'CGIHTTPRequestHandler'),
+    ('collections', 'UserList'): ('UserList', 'UserList'),
+    ('collections', 'UserString'): ('UserString', 'UserString'),
+    ('dbm', 'whichdb'): ('whichdb', 'whichdb'),
+    ('dbm', 'open'): ('anydbm', 'open'),
+})
diff -r cf5b910ac4c8 Lib/test/pickletester.py
--- a/Lib/test/pickletester.py	Sat Nov 15 10:58:58 2014 -0800
+++ b/Lib/test/pickletester.py	Sun Nov 16 22:46:48 2014 +0200
@@ -1,8 +1,9 @@
+import collections
 import copyreg
 import io
+import functools
 import pickle
 import pickletools
-import random
 import struct
 import sys
 import unittest
@@ -1636,6 +1637,48 @@ class AbstractPickleTests(unittest.TestC
                     unpickled = self.loads(self.dumps(method, proto))
                     self.assertEqual(method(*args), unpickled(*args))
 
+    def test_compat_pickle(self):
+        tests = [
+            (range(1, 7), '__builtin__', 'xrange'),
+            (map(int, '123'), 'itertools', 'imap'),
+            (Exception(), 'exceptions', 'Exception'),
+            (collections.UserDict(), 'UserDict', 'IterableUserDict'),
+            (collections.UserList(), 'UserList', 'UserList'),
+            (collections.defaultdict(), 'collections', 'defaultdict'),
+        ]
+        for val, mod, name in tests:
+            for proto in range(3):
+                with self.subTest(type=type(val), proto=proto):
+                    pickled = self.dumps(val, proto)
+                    self.assertIn(('c%s\n%s' % (mod, name)).encode(), pickled)
+                    self.assertIs(type(self.loads(pickled)), type(val))
+
+    def test_compat_unpickle(self):
+        # xrange(1, 7)
+        pickled = (b'\x80\x02c__builtin__\nxrange' +
+                   b'\nq\x00K\x01K\x07K\x01\x87q\x01Rq\x02.')
+        unpickled = self.loads(pickled)
+        self.assertIs(type(unpickled), range)
+        self.assertEqual(unpickled, range(1, 7))
+        self.assertEqual(list(unpickled), [1, 2, 3, 4, 5, 6])
+        # reduce
+        pickled = b'\x80\x02c__builtin__\nreduce\nq\x00.'
+        self.assertIs(self.loads(pickled), functools.reduce)
+        # Exception(), StandardError()
+        for name in (b'Exception', b'StandardError'):
+            pickled = (b'\x80\x02cexceptions\n' + name +
+                       b'\nq\x00U\x03ughq\x01\x85q\x02Rq\x03.')
+            unpickled = self.loads(pickled)
+            self.assertIs(type(unpickled), Exception)
+            self.assertEqual(str(unpickled), 'ugh')
+        # UserDict.UserDict({1: 2}), UserDict.IterableUserDict({1: 2})
+        for name in (b'UserDict', b'IterableUserDict'):
+            pickled = (b'\x80\x02(cUserDict\n' + name +
+                       b'\nq\x00oq\x01}q\x02U\x04dataq\x03}q\x04K\x01K\x02ssb.')
+            unpickled = self.loads(pickled)
+            self.assertIs(type(unpickled), collections.UserDict)
+            self.assertEqual(unpickled, collections.UserDict({1: 2}))
+
 
 class BigmemPickleTests(unittest.TestCase):