use mysql for mailman3

Question

I set up mailman3 using the mailman-suite configuration. I expected that mailman uses the database provided there (like sqlite or mysql), but it seems to have its own database file mailman.db in var/data. I followed the instructions here and added

[database]
class: mailman.database.mysql.MySQLDatabase
url: mysql+pymysql://myuser:mypassword@mymysqlhost/mailman?charset=utf8&use_unicode=1

to my mailman.cfg. Of course I replaced myuser, mypassword, mymysqlhost with the correct data. But still, mailman3 uses the data from mailman.db

What do I have to do to make mailman use the mysql database?