two improvements mailman web install
caa19fcb:
Mailman Web’s documentation explain how to change the path for settings.py.
In the virtualenv.rst there is no information/hint about it yet.
5187bd01:
According to Django for Mailman Admins mailman-web
command defaults the settings.py to be present at /etc/mailman3/settings.py and automatically sets up the PYTHONPATH for Django to be able to import -> arguments --settings --pythonpath are not necessary anymore.
Adding caa19fcb before is important for explanation if a custom path is choosen (imo).