Set up database

            Creates tables required for the authentication module.

def _create_database(self):
        """ Set up database

            Creates tables required for the authentication module.
        """

        self._logger.info('creating user database')
        sql = '''CREATE TABLE IF NOT EXISTS user (
            username NOT NULL PRIMARY KEY,
            pwd_salt NOT NULL,
            pwd_hash NOT NULL,
            full_name,
            trusted NOT NULL DEFAULT 0,
            readonly NOT NULL DEFAULT 0
        )'''
        self._db_curs.execute(sql)
        self._db_conn.commit()