Tests that parse argparse --help: the 'options:' heading is Python 3.10+, 3.9 prints 'optional arguments:'

If a test slices prog --help output starting at the 'options:' heading, it breaks on Python 3.9. Python 3.10 renamed argparse's 'optional arguments:' section to 'options:', so on 3.9 s.find('options:') returns -1. A follow-up such as s.find(x, -1) then searches only the last character, so the check fails with a confusing one-character slice like 'S'. It passes on a 3.10+ dev machine and fails on 3.9 servers (e.g. RHEL 9 system python 3.9).

Robust options: - Find the option's own entry rather than the section heading. The usage line also mentions the option, so use s.rfind('--opt METAVAR') to get the help entry, not the usage line. - Or read the help string directly from the parser object: next(a for a in parser._actions if '--opt' in a.option_strings).help.

Normalise whitespace before matching phrases, because argparse rewraps help text to the terminal width (' '.join(s.split())).