[3.12] gh-85935: Improve tests for invalid arguments in test_argparse (GH-124891) (GH-124898)

Check also specific error messages.
(cherry picked from commit 2c050d4bc28bffd2990b5a0bd03fb6fc56b13656)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>