Remove Python 2 compatibility cruft from unittest.mock

Lib/unittest/mock.py

@@ -1,5 +1,8 @@
 # mock.py
 # Test tools for mocking and patching.
+# Maintained by Michael Foord
+# Backport for other versions of Python available from
+# http://pypi.python.org/pypi/mock
 
 __all__ = (
     'Mock',
@@ -259,11 +262,6 @@ def __getattr__(self, name):
 _deleted = sentinel.DELETED
 
 
-class OldStyleClass:
-    pass
-ClassType = type(OldStyleClass)
-
-
 def _copy(value):
     if type(value) in (dict, list, tuple, set):
         return type(value)(value)