We need to provide an empty sites.db sqlite3 database if missing. For that, I see two solutions:
1. through Salt
phpbb_saas_sites: cmd.run: - name: echo "CREATE TABLE sites (id text, host text, db_user text, db_password text, db_prefix, active boolean);" | sqlite3 -batch /srv/phpbb/sites/sites.db - creates: /srv/phpbb/sites/sites.db
2. through the phpBB wrapper
phpbb_saas_sites: cmd.run: - name: phpbb initialize-sites-db - creates: /srv/phpbb/sites/sites.db
And add an initialize-sites-db command to call sqlite3.