The difference in the errors below is the reason the systematic fix in Benjamin's patch simply wasn't practical in 2.x (as it would have required a complex deprecation dance to turn None, True and False into real keywords):

Python 2.7.3 (default, Jul 24 2012, 10:05:38) 
[GCC 4.7.0 20120507 (Red Hat 4.7.0-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class C: pass
... 
>>> C.None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: class C has no attribute 'None'
>>> 

Python 3.2.3 (default, Jun  8 2012, 05:36:09) 
[GCC 4.7.0 20120507 (Red Hat 4.7.0-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class C: pass
... 
>>> C.None
  File "<stdin>", line 1
    C.None
         ^
SyntaxError: invalid syntax