Some content of The Contributor Guide needs to be updated.
The Contributor Guide: https://docs.mailman3.org/en/latest/devsetup.html#set-up-django-mailman3 ‘To run the tests: $ tox -e py37-django21‘ This instruction needs to be updated. At first, I made an error when running. I checked tox.ini. It is found that only django22 and later versions can be used for testing. So I suggest updating this instruction. The same issue also occurs in ‘Set up and run Postorius’ and ‘Set up and run HyperKitty’.