Curse me for a fool.  I reported this exact same thing
in getattr but failed to
look 30 lines down to notice hasattr.

hasattr(foo, 'bar') catches all exceptions.  I think it
should only catch 
AttributeError.  Example:

>>> class Foo:
...     def __getattr__(self, attr):
...         assert 0
... 
>>> f = Foo()
>>> hasattr(f, 'bar')
0               # should have gotten an AssertionError
>>>

This patch makes hasattr only catch AttributeError.  I
changed the 
docstring to reflect that, and also changed the getattr
docstring
to read a little more naturally.

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(The patch seems to be reversed.)
The patch otherwise looks fine to me, but it will break 
code that depends on the current behavior.
It can be argued that if getattr() raises *any* error, the 
attr doesn't exist, so the current behavior is in fact 
correct.

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That's true, but the current behavior can mask bugs
unexpectedly.  For example, if you ask someone if the
brakes are engaged, and they discover that the brakes have
crumbled to dust and fallen off, you probably want a
different answer than "no". :)

getattr() (now) only catches AttributeErrors, so there's 
a consistency thing too.

Anyway, it's your call :)

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This looks like a possibly worthwhile semantic change.  In
order to help this patch progress I would recommend you to
raise the question in python-dev.

The library documentation should also be patched to reflect
the change.

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Sorry, I'm rejecting this, at Guido's request.  I agree:  far too 
much code would break if this were to change now; if you 
want hasattr()-like functionality that passes on "unexpected" 
exceptions, you can get it now via doing getattr(obj, attr, 
None); and, most fundamentally, it's part of hasattr's contract 
(design) that it never raises an exception.

For the record, this was eventually fixed for Python 3.2.  See 
http://bugs.python.org/issue9666.

Adding this here because issue504714 comes up earlier than issue9666 in many web searches.