Another issue on AMD64 Fedora Rawhide Refleaks 3.7 where test_map_chunksize() hangs.

https://buildbot.python.org/all/#/builders/133/builds/18

(...)
test_initializer (test.test_concurrent_futures.ProcessPoolForkInitializerTest) ... 0.13s ok
test_free_reference (test.test_concurrent_futures.ProcessPoolForkProcessPoolExecutorTest) ... 0.17s ok
test_killed_child (test.test_concurrent_futures.ProcessPoolForkProcessPoolExecutorTest) ... 0.15s ok
test_map (test.test_concurrent_futures.ProcessPoolForkProcessPoolExecutorTest) ... 0.17s ok
.....Timeout (3:15:00)!
Thread 0x00007f095aa00700 (most recent call first):
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 296 in wait
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/multiprocessing/queues.py", line 224 in _feed
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 870 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 926 in _bootstrap_inner
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 890 in _bootstrap

Thread 0x00007f095a1ff700 (most recent call first):
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/selectors.py", line 415 in select
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/multiprocessing/connection.py", line 920 in wait
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/concurrent/futures/process.py", line 361 in _queue_management_worker
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 870 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 926 in _bootstrap_inner
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 890 in _bootstrap

Thread 0x00007f096a552740 (most recent call first):
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/threading.py", line 296 in wait
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/concurrent/futures/_base.py", line 430 in result
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/concurrent/futures/_base.py", line 598 in result_iterator
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/concurrent/futures/process.py", line 483 in _chain_from_iterable_of_lists
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/test_concurrent_futures.py", line 782 in test_map_chunksize
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/case.py", line 628 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/case.py", line 676 in __call__
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 122 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 84 in __call__
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 122 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 84 in __call__
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 122 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/suite.py", line 84 in __call__
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/unittest/runner.py", line 176 in run
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/support/__init__.py", line 1919 in _run_suite
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/support/__init__.py", line 2015 in run_unittest
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/test_concurrent_futures.py", line 1245 in test_main
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/support/__init__.py", line 2147 in decorator
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/refleak.py", line 87 in dash_R
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/runtest.py", line 232 in _runtest_inner2
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/runtest.py", line 270 in _runtest_inner
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/runtest.py", line 154 in _runtest
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/runtest.py", line 193 in runtest
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/main.py", line 313 in rerun_failed_tests
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/main.py", line 685 in _main
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/main.py", line 629 in main
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/libregrtest/main.py", line 706 in main
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/test/__main__.py", line 2 in <module>
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/runpy.py", line 85 in _run_code
  File "/home/buildbot/buildarea/3.7.cstratak-fedora-rawhide-x86_64.refleak/build/Lib/runpy.py", line 193 in _run_module_as_main