logrotate: invoke reopen as "list" user
logrotate's "reopen" invocation will fail if mailman is run as the root user, and the backend database doesn't provide access to the superuser.
For example, if mailman is connected to a postgresql database, the credentials to connect to the database might not be immediately available to the superuser, resulting in errors like:
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) \
FATAL: role "root" does not exist