The traceback message given when trying to hash unhashable objects has
changed from Python 2.5 to 2.6:

Python 2.5.2a0 (r251:54863, Feb 10 2008, 01:31:28) 
>>> hash([])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list objects are unhashable

Python 2.6a1 (r26a1:61143, Mar 25 2008, 19:41:30) 
>>> hash([])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'

This breaks my Doctests unless I add a somewhat ugly "# doctest:
+IGNORE_EXCEPTION_DETAIL" comment, so if this is not done on purpose, I
would prefer Python 2.6 to output the same as 2.5.