Issue #12209: Minor edits to faulthandler doc. Patch written by Éric Araujo.
Issue #21038: Cleanup test_epoll.py

Remove useless test and unused variables. Initial patch by Andreas Schwab.
Issue #21038: Use monotonic clock to compute timeout, not the system clock
Issue #21058: fix typo in a comment. Patch written by Vajrasky Kok.
backport: #20145: assert[Raises|Warns]Regex now raise TypeError on bad regex.

Previously a non-string, non-regex second argument and missing callable
argument could cause the test to appear to always pass.

Initial patch by Kamilla Holanda.