Flaky test - PySparkInterpreterTest.testCompletion

testCompletion(org.apache.zeppelin.spark.PySparkInterpreterTest)  Time elapsed: 0.102 sec  <<< FAILURE!
java.lang.AssertionError: null
	at org.junit.Assert.fail(Assert.java:86)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.junit.Assert.assertTrue(Assert.java:52)
	at org.apache.zeppelin.spark.PySparkInterpreterTest.testCompletion(PySparkInterpreterTest.java:121)

17/01/26 19:23:23 INFO SparkContext: Invoking stop() from shutdown hook
17/01/26 19:23:23 INFO SparkUI: Stopped Spark web UI at http://172.17.0.6:4040
17/01/26 19:23:23 INFO MapOutputTrackerMasterEndpoint: MapOutputTrackerMasterEndpoint stopped!
17/01/26 19:23:23 INFO MemoryStore: MemoryStore cleared
17/01/26 19:23:23 INFO BlockManager: BlockManager stopped
17/01/26 19:23:23 INFO BlockManagerMaster: BlockManagerMaster stopped
17/01/26 19:23:23 INFO OutputCommitCoordinator$OutputCommitCoordinatorEndpoint: OutputCommitCoordinator stopped!
17/01/26 19:23:23 INFO RemoteActorRefProvider$RemotingTerminator: Shutting down remote daemon.
17/01/26 19:23:23 INFO SparkContext: Successfully stopped SparkContext
17/01/26 19:23:23 INFO ShutdownHookManager: Shutdown hook called
17/01/26 19:23:23 INFO ShutdownHookManager: Deleting directory /tmp/spark-416c693f-9290-428b-830a-d0bb5c0da703/pyspark-6c48736e-37c2-4747-8a38-5d0bf104b4fa
17/01/26 19:23:23 INFO ShutdownHookManager: Deleting directory /tmp/spark-9ce929d5-8400-410d-9729-9a3caefd8b2c
17/01/26 19:23:23 INFO RemoteActorRefProvider$RemotingTerminator: Remote daemon shut down; proceeding with flushing remote transports.
17/01/26 19:23:23 INFO ShutdownHookManager: Deleting directory /tmp/spark-508bdc3a-9777-486b-901b-b72d0ba42250
17/01/26 19:23:23 INFO ShutdownHookManager: Deleting directory /tmp/spark-416c693f-9290-428b-830a-d0bb5c0da703

Results :

Failed tests: 
  PySparkInterpreterTest.testCompletion:121 null

Tests run: 7, Failures: 1, Errors: 0, Skipped: 0