* bpo-30523: regrtest --list-cases --match (#2401)
* regrtest --list-cases now supports --match and --match-file options.
Example: ./python -m test --list-cases -m FileTests test_os
* --list-cases now also sets support.verbose to False to prevent
messages to stdout when loading test modules.
* Add support._match_test() private function.
(cherry picked from commit ace56d5836)
* bpo-30764: regrtest: add --fail-env-changed option (#2402)
* bpo-30764: regrtest: change exit code on failure
* Exit code 2 if failed tests ("bad")
* Exit code 3 if interrupted
* bpo-30764: regrtest: add --fail-env-changed option
If the option is set, mark a test as failed if it alters the
environment, for example if it creates a file without removing it.
(cherry picked from commit 63f54c6893)
* bpo-30776: reduce regrtest -R false positives (#2422)
* Change the regrtest --huntrleaks checker to decide if a test file
leaks or not. Require that each run leaks at least 1 reference.
* Warmup runs are now completely ignored: ignored in the checker test
and not used anymore to compute the sum.
* Add an unit test for a reference leak.
Example of reference differences previously considered a failure
(leak) and now considered as success (success, no leak):
[3, 0, 0]
[0, 1, 0]
[8, -8, 1]
(cherry picked from commit 48b5c422ff)
* Fix "-m test --forever": replace _test_forever() with self._test_forever()
* Add unit test for --forever
* Add unit test for a failing test
* Fix also some pyflakes warnings in libregrtest
