[3.6] bpo-30845: Enhance test_concurrent_futures cleanup (#2564) by vstinner · Pull Request #2880 · python/cpython
In setUp() and tearDown() methods of test_concurrent_futures tests,
make sure that tests don't leak threads nor processes. Clear
explicitly the reference to the executor to make it that it's
destroyed (to prevent "dangling threads" warning).
(cherry picked from commit 3df9dec)