test_tools.test_sundry() now uses an unittest mock to prevent the
logging module to register a real "atfork" function which kept the
logging module dictionary alive. So the logging module can be
properly unloaded. Previously, the logging module was loaded before
test_sundry(), but it's no longer the case since recent test_tools
sub-tests removals.
Instead of explicitly enumerate test classes for run_unittest()
use the unittest ability to discover tests. This also makes these
tests discoverable and runnable with unittest.
load_tests() can be used for dynamic generating tests and adding
doctests. setUpModule(), tearDownModule() and addModuleCleanup()
can be used for running code before and after all module tests.
Move `threaded_import_hangers`, a dependency of `test_threaded_import`, to the directory `test_importlib/`. Also update the import references for `threaded_import_hangers` in `test_threaded_import`.
https://bugs.python.org/issue19696
