Sorry for being AWOL for so long. Attached is a patch that doesn't install a handler and checks stderr for the exception output. Unfortunately, it looks like the logging tests are still messing things up:

./python.exe -m test test_concurrent_futures test_concurrent_futures
[1/2] test_concurrent_futures
[2/2] test_concurrent_futures
All 2 tests OK.

% ./python.exe -m test test_concurrent_futures test_logging test_concurrent_futures
[1/3] test_concurrent_futures
[2/3] test_logging
[3/3] test_concurrent_futures
test test_concurrent_futures failed -- Traceback (most recent call last):
  File "/home/bquinlan/shared/py3k/Lib/test/test_concurrent_futures.py", line 642, in test_done_callback_raises
    self.assertIn('Exception: doh!', stderr.getvalue())
AssertionError: 'Exception: doh!' not found in ''

2 tests OK.
1 test failed:
    test_concurrent_futures