On AMD64 FreeBSD Shared 3.8 which is know to be very slow, different test_concurrent_futures tests failed.

https://buildbot.python.org/all/#builders/374/builds/3

test_concurrent_futures was run twice. Once in parallel of other tests, then alone in sequence.


The first run emitted two "threading_cleanup() failed" warnings and test_idle_thread_reuse() failed:

test_idle_thread_reuse (test.test_concurrent_futures.ThreadPoolExecutorTest) ... 1.05s Warning -- threading_cleanup() failed to cleanup 2 threads (count: 2, dangling: 3)
test_map (test.test_concurrent_futures.ThreadPoolExecutorTest) ... 3.80s Warning -- threading_cleanup() failed to cleanup -2 threads (count: 0, dangling: 1)

FAIL: test_idle_thread_reuse (test.test_concurrent_futures.ThreadPoolExecutorTest)
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Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/test/test_concurrent_futures.py", line 782, in test_idle_thread_reuse
    self.assertEqual(len(executor._threads), 1)
AssertionError: 2 != 1

At the second run, test_free_reference() failed:

1:15:08 load avg: 9.24 Re-running test_concurrent_futures in verbose mode

FAIL: test_free_reference (test.test_concurrent_futures.ThreadPoolExecutorTest)
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Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/test/test_concurrent_futures.py", line 745, in test_free_reference
    self.assertIsNone(wr())
AssertionError: <test.test_concurrent_futures.MyObject object at 0x8031cc780> is not None