Changes in Python 3.14.3 break cmd2

[tleonhardt]

Error:

______________________________ ERROR collecting tests/test_argparse_completer.py _______________________________
tests/test_argparse_completer.py:42: in <module>
    class ArgparseCompleterTester(cmd2.Cmd):
tests/test_argparse_completer.py:303: in ArgparseCompleterTester
    arg_tokens_subparser = arg_tokens_parser.add_subparsers(dest='subcommand')
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
cmd2/argparse_custom.py:1509: in add_subparsers
    return super().add_subparsers(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../.local/share/uv/python/cpython-3.14.3-macos-aarch64-none/lib/python3.14/argparse.py:1968: in add_subparsers
    formatter.add_usage(None, positionals, groups, '')
.venv/lib/python3.14/site-packages/rich_argparse/_argparse.py:232: in add_usage
    usage_text = _strip_codes(self._format_usage(usage, actions, groups, prefix=prefix))
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
cmd2/argparse_custom.py:1172: in _format_usage
    format_actions = self._format_actions_usage
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
E   AttributeError: 'Cmd2HelpFormatter' object has no attribute '_format_actions_usage'
=========================================== short test summary info ============================================
ERROR tests/test_argparse_completer.py - AttributeError: 'Cmd2HelpFormatter' object has no attribute '_format_actions_usage'
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
=============================================== 1 error in 0.18s ===============================================

[github-actions]

🤖 Hi @tleonhardt, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[tleonhardt]

Whatever the fix is we'll have to make on both the main and 3.x branches.

[tleonhardt]

I'm thinking we actually need to create an issue for rich_argparse to make sure that module properly supports Python 3.14.3 in general and for the RichHelpFormatter in particular.

Another option might be to remove some of our custom formatting.

[tleonhardt]

PR #1571 addresses this issue for the 3.x branch. Once that merges in, we'll need to cherry-pick changes to a branch intended to marge into main.