To clarify, here's the bug:  the following code should raise an exception, but doesn't:

iwasawa:cpython mdickinson$ ./python.exe -3
Python 2.7.3+ (2.7:333fe4c4897a, Nov 17 2012, 18:01:00) 
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import warnings; warnings.filterwarnings("error")
>>> class A(object):
...     def __eq__(self, other):
...         return False
... 


Without "warnings.filterwarnings("error")", the warning gets issued as expected:

iwasawa:cpython mdickinson$ ./python.exe -3
Python 2.7.3+ (2.7:333fe4c4897a, Nov 17 2012, 18:01:00) 
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> class A(object):
...     def __eq__(self, object):
...         return False
... 
__main__:1: DeprecationWarning: Overriding __eq__ blocks inheritance of __hash__ in 3.x

Brett, is it okay to re-open this?  Perhaps a change of title would help?  Or I can open a new issue for the remaining problem, if you think that's better.