YarnShuffleIntegrationSuite fails when SPARK_PREPEND_CLASSES set to 1.
Normally mllib built before yarn module. When SPARK_PREPEND_CLASSES used mllib classes are on yarn test classpath.
Before 2.3 that did not cause issues. But 2.3 has
SPARK-22450, which registered some mllib classes with the kryo serializer. Now it dies with the following error: