borgbackup fails to build with Python 3.15.0a3.

4 tests errored with the same issue:

_________________ ERROR collecting borg/testsuite/archiver.py __________________
/usr/lib64/python3.15/argparse.py:1792: in _check_help
    formatter._expand_help(action)
/usr/lib64/python3.15/argparse.py:695: in _expand_help
    return help_string % params
           ^^^^^^^^^^^^^^^^^^^^
E   TypeError: %o format: an integer is required, not str

The above exception was the direct cause of the following exception:
borg/testsuite/archiver.py:5344: in <module>
    @pytest.mark.parametrize('command, parser', list(get_all_parsers().items()))
                                                     ^^^^^^^^^^^^^^^^^
borg/testsuite/archiver.py:5321: in get_all_parsers
    parser = Archiver(prog='borg').build_parser()
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
borg/archiver.py:3850: in build_parser
    subparser.add_argument('--stdin-mode', metavar='M', dest='stdin_mode', type=lambda s: int(s, 8), default=STDIN_MODE_DEFAULT,
/usr/lib64/python3.15/argparse.py:1600: in add_argument
    self._check_help(action)
/usr/lib64/python3.15/argparse.py:1794: in _check_help
    raise ValueError('badly formed help string') from exc
E   ValueError: badly formed help string

https://docs.python.org/3.15/whatsnew/3.15.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.15/fedora-rawhide-x86_64/09935190-borgbackup/

For all our attempts to build borgbackup with Python 3.15, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.15/package/borgbackup/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.15:
https://copr.fedorainfracloud.org/coprs/g/python/python3.15/

Let us know here if you have any questions.

Python 3.15 is planned to be included in Fedora 45.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.15.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.