Connect Otree Project to MySQL

Question

I'm trying to connect my Otree project to MySQL database, but whatever I do it doesn't replace the default database (which is SQLite) with MySQL. When I run the command otree runprodserver 80 and try to access localhost:80 I get the following message:

Your database is not ready. Try running 'otree resetdb'. (Missing tables for otree.FailedSessionCreation, otree.ChatMessage, sessions.Session, and 15 other models).

(obviously running 'otree resetdb' does not solve the problem.)

I added the following lines to settings.py :

environ['DATABASE_URL'] = 'mysql://localhost:3306'

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'DBNAME',
        'USER': 'DBUSER',
        'PASSWORD': 'DBPASSWORD',
        'HOST': 'localhost',
        'PORT': '3306',
    }
}

but it still doesn't work. Any ideas what can I do to solve the problem? Thanks.