Even more, Python 3.0 crashes from following code:
Python 3.0b1+ (py3k:64528M, Jun 26 2008, 11:40:20)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from warnings import warn_explicit
>>> warn_explicit(None, UserWarning, None, 0, None, None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: Objects/dictobject.c:709: bad argument to internal function
>>> warn_explicit(None, UserWarning, None, 0, None, {})
Segmentation fault