Hello.

python-towncrier fails to build from source becasue it uses one or both of:

 - %pyproject_buildrequires -t/-e (generate dependencies via tox)
 - %tox (run tox)

without tox configuration (e.g. tox.ini or tox section of pyproject.toml/setup.cfg).

This was always supposed to fail, but regressed with tox 4.
Now it fails again.

https://lists.fedoraproject.org/archives/list/python-devel@lists.fedoraproject.org/thread/ZSHSHZKVA4XJQBJD7FMMCALKN4UP5SAJ/
https://lists.fedoraproject.org/archives/list/devel-announce@lists.fedoraproject.org/thread/N25A2BER3RUHMTBIULQ6AVWRILSL5VGW/

If this package uses tox upstream, make sure to use a source tarball that includes the tox configuration (e.g. an archive from GitHub instead of sdist from PyPI).

If this package does not use tox upstream, you cannot use the tox options.
If your package uses %pyproject_buildrequires -t/-e but does not use %tox, just drop the -t/-e option.
If your package uses %tox, replace the call with a more suitable way for running tests (e.g. %pytest).

Let me know if you need assistance. Thanks.