The changeset 223731925d06 of the issue issue #28082 "use IntFlag for re constants" made Python startup 34% slower:
- rev 5637c9b4dd4c: Median +- std dev: 19.5 ms +- 0.0 ms
- rev 223731925d06: Median +- std dev: 26.2 ms +- 0.0 ms
The change adds "import enum" in Lib/re.py, so the enum module is imported, whereas it wasn't before. It seems like importing enum takes 6.7 ms.
I propose to revert the change 223731925d06 in Python 3.6 and reopen the issue #28082 to try to find another solution for the re module which doesn't impact Python startup performance.