This is tricky. Note the sys.path hack in test/unit/__init__.py where
we intentionally use the Fedora's default Python libraries with a
different Python version selected by Tox. Right now it means that we
use, e.g., python3-rpm compiled for Python 3.12 (F39) with Python 3.7
(which probably works because Tox is executed as root in the tox
container, overwriting the pre-compiled *.pyc files in container).
Some tests need to be skipped in Tox, therefore the skip_if_tox()
method.
Also, the GitHub's action for 'git checkout' provides somewhat
non-standard environment for Tito to work, hence the fix_tox_env()
configuration method.
