bpo-40903: Handle multiple '=' in invalid assignment rules in the PEG parser (GH-20697)


Automerge-Triggered-By: @pablogsal
(cherry picked from commit 9f495908c5bd3645ed1af82d7bae6782720dab77)

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
5 files changed