Since then, Senthil Kumaran converted test_urllib2_localnet (and another urllib test or two) to unittest.main, using this:

"""
threads_key = None

def setUpModule():
    # Store the threading_setup in a key and ensure that it is cleaned up
    # in the tearDown
    global threads_key
    threads_key = support.threading_setup()

def tearDownModule():
    if threads_key:
        support.threading_cleanup(threads_key)

if __name__ == "__main__":
    unittest.main()
"""

Since nobody has said anything against that in the two months since it was done, that's what I was going to go with when I got back to this; support.reap_children() can just be called in tearDownModule.  If you'd like to provide a patch, Mark, please do so!