Map a database name to the Cluster that holds the database.

        Args:
            dbname: A database name.

        Returns:
            A dict containing the information about the Cluster that holds the
            database.

def _match_dbname(self, dbname):
        """Map a database name to the Cluster that holds the database.

        Args:
            dbname: A database name.

        Returns:
            A dict containing the information about the Cluster that holds the
            database.
        """
        for config in self._clusters:
            if re.match(config['pattern'], dbname):
                return config
        raise Exception('No such database %s.' % dbname)