Three pytest key contributors to have quit the project due to a single bad actor

Two contributors have announced their departures on the pytest-dev mailing list:

- https://mail.python.org/pipermail/pytest-dev/2020-April/0049...

- https://mail.python.org/pipermail/pytest-dev/2020-April/0049...

Other threads: https://news.ycombinator.com/item?id=22837373 and https://news.ycombinator.com/item?id=22839902