bpo-28146: Fix a confusing error message in str.format() (GH-24213)


Automerge-Triggered-By: GH:pitrou
(cherry picked from commit 4aeee0b47b3a2b604bbac37040320ffc88c291f2)

Co-authored-by: Irit Katriel <iritkatriel@yahoo.com>
3 files changed