I already opened a debian bugreport for it, but I'm still wondering why
the following issue appears:
line 30, in <module>
'Did you install mysqlclient or MySQL-python?' % e
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb
module: No module named 'MySQLdb'.
Did you install mysqlclient or MySQL-python?
python3-pymysql, which is a dependency of mailman3-web and provides
mySQLdb, is installed.
(Maybe it's time to migrate to postgres.)