diff -r 136adbcefa5f Lib/_compat_pickle.py
--- a/Lib/_compat_pickle.py	Sun Jan 03 18:00:31 2016 -0800
+++ b/Lib/_compat_pickle.py	Tue Jan 05 11:17:41 2016 +0200
@@ -177,6 +177,13 @@ IMPORT_MAPPING.update({
     'DocXMLRPCServer': 'xmlrpc.server',
     'SimpleHTTPServer': 'http.server',
     'CGIHTTPServer': 'http.server',
+    # For compatibility with broken pickles saved in old Python 3 versions
+    'UserDict': 'collections',
+    'UserList': 'collections',
+    'UserString': 'collections',
+    'whichdb': 'dbm',
+    'StringIO':  'io',
+    'cStringIO': 'io',
 })
 
 REVERSE_IMPORT_MAPPING.update({