gh-119949: Refactor test_exc() helper in test_format.py (GH-135452)

Use assertRaisesRegex() context and fix
https://github.com/python/cpython/pull/119781#pullrequestreview-2088240959

* address review: minimize diff

Sergey B Kirpichev committed 1d ago

0851700a9d99ca4bebd8d5f9d73c8c9ab1084405

Parent: a38804b

Committed by GitHub <noreply@github.com> on 5/24/2026, 10:24:59 AM