Python dtest TestWriteFailures.test_paxos is failing with Paxos V2

test_paxos
write_failures_test.TestWriteFailures

self = <write_failures_test.TestWriteFailures object at 0x7f396bb68910>

    def test_paxos(self):
        """
        A light transaction receives a WriteFailure
        """
>       exc = self._perform_cql_statement("INSERT INTO mytable (key, value) VALUES ('key1', 'Value 1') IF NOT EXISTS")

write_failures_test.py:202: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
write_failures_test.py:88: in _perform_cql_statement
    session.execute(statement)
../env3.7/src/cassandra-driver/cassandra/cluster.py:2618: in execute
    return self.execute_async(query, parameters, trace, custom_payload, timeout, execution_profile, paging_state, host, execute_as).result()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <ResponseFuture: query='<BoundStatement query="INSERT INTO mytable (key, value) VALUES ('key1', 'Value 1') IF NOT EXIS...ncy': 'SERIAL', 'required_responses': 2, 'received_responses': 1, 'write_type': 'CAS'} coordinator_host=127.0.0.1:9042>

    def result(self):
        """
        Return the final result or raise an Exception if errors were
        encountered.  If the final result or error has not been set
        yet, this method will block until it is set, or the timeout
        set for the request expires.
    
        Timeout is specified in the Session request execution functions.
        If the timeout is exceeded, an :exc:`cassandra.OperationTimedOut` will be raised.
        This is a client-side timeout. For more information
        about server-side coordinator timeouts, see :class:`.policies.RetryPolicy`.
    
        Example usage::
    
            >>> future = session.execute_async("SELECT * FROM mycf")
            >>> # do other stuff...
    
            >>> try:
            ...     rows = future.result()
            ...     for row in rows:
            ...         ... # process results
            ... except Exception:
            ...     log.exception("Operation failed:")
    
        """
        self._event.wait()
        if self._final_result is not _NOT_SET:
            return ResultSet(self, self._final_result)
        else:
>           raise self._final_exception
E           cassandra.WriteTimeout: Error from server: code=1100 [Coordinator node timed out waiting for replica nodes' responses] message="CAS operation timed out: received 1 of 2 required responses after 0 contention retries" info={'consistency': 'SERIAL', 'required_responses': 2, 'received_responses': 1, 'write_type': 'CAS'}

../env3.7/src/cassandra-driver/cassandra/cluster.py:4894: WriteTimeout