[3.12] gh-117467: Add preserving of mailbox owner on flush (GH-117510)#117537

serhiy-storchaka merged 1 commit intopython:3.12python/cpython:3.12from

miss-islington:backport-3f5bcc8-3.12miss-islington/cpython:backport-3f5bcc8-3.12Copy head branch name to clipboard