get rid of 'test left new threads behind' messages during 'make check'

[Elliot Murphy]

This seems to be an error reported by Zope.

sourcecode/zope/src/zope/testing/testrunner.py has this code:
# Did the test leave any new threads behind?
        new_threads = [t for t in threading.enumerate()
                         if (t.isAlive()
                             and
                             t not in self._threads)]
        if new_threads:
            print "The following test left new threads behind:"
            print test
            print "New thread(s):", new_threads

sourcecode/zope/src/ZEO/tests/ConnectionTests.py has this code:
 # Get rid of the 'test left new threads behind' warning
        time.sleep(0.1)

yuck!

While running 'make check' on a multiprocessor machine, I get plenty of these messages about test leaving threads behind. Here is an example:
The following test left new threads behind:
 test_probe_sets_up_timeout_call (canonical.launchpad.scripts.ftests.test_distributionmirror_prober.TestProberProtocol)
 New thread(s): [<Thread(PoolThread-46912704483056-1, started)>]
     test_redirectawareprober_detects_infinite_loop (canonical.launchpad.scripts.ftests.test_distributionmirror_prober.TestProberProtocol)

It would be good to clean these up (without resorting to sleep calls).

[Robert Collins (lifeless)]

paste has a facility to kill threads, could grab that and use it.