`pytest` requires `pluggy<0.7,>=0.5` and `py>=1.5.0`.
Since `python-test` jobs use a Docker image that installs
`tox_requirements`, and the system packages are used (due to `zstandard`
existing), we need to ensure compatibility.
Depends on D132082
Differential Revision: https://phabricator.services.mozilla.com/D134451