ot support adding nullable columns
</li>
<li>[<a href='https://issues.apache.org/jira/browse/FLINK-20183'>FLINK-20183</a>] -         Fix the default PYTHONPATH is overwritten in client side
</li>
<li>[<a href='https://issues.apache.org/jira/browse/FLINK-20193'>FLINK-20193</a>] -         SourceCoordinator should catch exception thrown from SplitEnumerator.start()
</li>
<li>[<a href='https://issues.apache.org/jira/browse/FLINK-20194'>FLINK-20194</a>] -         KafkaSourceFetcherManager.commitOffsets() should 