The docs at http://docs.python.org/lib/node346.html say
this:
"""
class StreamHandler(  	[strm])
    Returns a new instance of the StreamHandler class.
If strm is specified, the instance will use it for
logging output; otherwise, sys.stderr will be used.
"""

However, that's not quite true.
StreamHandler.__init__() actually tests for truth of
strm, which means you have to be careful that strm does
not happen to evaluate to boolean false.

My use case: I'm writing some tests that verify that
certain methods put certain strings into the logs. So
my setUp() adds a StreamHandler with its stream set to
an instance of this trivial class:

class FakeLog(list):
    def write(self, msg):
        self.append(msg)
    def flush(self):
        pass

... which does not work, because an empty list
evaluates to false, so my handler writes to stderr even
though i told it not to.  It's trivial to work around
this by adding a __nonzero__ method, but the need to do
so is certainly not clear from the docs. Therefore imho
this is a bug. The patch is trivial, and is attached.

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Vinay, any comments?  We are preparing for 2.5 alpha1 within
a day.  There will be freeze real soon now.

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Fix checked into Subversion.