QA:

```
$ nox -s tests_packaging
nox > Running session tests_packaging
nox > Creating virtual environment (virtualenv) using python3 in .nox/tests_packaging
nox > python -m pip install -r tests/requirements.txt --prefer-binary
nox > pytest tests/extra_python_package
=========================================================== test session starts ============================================================
platform darwin -- Python 3.10.2, pytest-7.0.0, pluggy-1.5.0
rootdir: /Users/rgrossekunst/forked/pybind11/tests/extra_python_package, configfile: pytest.ini
plugins: timeout-2.3.1
collected 4 items

tests/extra_python_package/test_files.py ....                                                                                        [100%]

============================================================ 4 passed in 33.98s ============================================================
nox > Session tests_packaging was successful.
```