I found that my testing using tox fails because of missing sphinx. This is because the tox configuration in https://github.com/bagel897/pytoolconfig/blob/main/pyproject.toml does not properly list test dependencies. There is an attempt to list deps using the groups keyword:

[testenv]
groups = test, doc, global
commands = pytest

but tox does not recognise this option - see https://tox.wiki/en/stable/config.html
There are dependency_groups, extras, and deps options that should be used to list test dependencies.