Retrieve a dict containing Cassandra client config params.

def _get_cassandra_config(self):
        """Retrieve a dict containing Cassandra client config params."""
        parts = urlsplit(os.environ.get('CASSANDRA_URI', DEFAULT_URI))
        if parts.scheme != 'cassandra':
            raise RuntimeError(
                'CASSANDRA_URI scheme is not "cassandra://"!')

        _, _, ip_addresses = socket.gethostbyname_ex(parts.hostname)
        if not ip_addresses:
            raise RuntimeError('Unable to find Cassandra in DNS!')

        return {
            'contact_points': ip_addresses,
            'port': parts.port or DEFAULT_PORT,
        }