Fix test_importlib.test_side_effect_import() (GH-104840)
Wait until the thread spawn by the import completes to avoid dangling
threads. With this fix, the following command no longer fails:
./python -m test --fail-env-changed test_importlib -m test_side_effect_import -F -j20
(cherry picked from commit 426950993f)
Co-authored-by: Victor Stinner <vstinner@python.org>
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
