YarnShuffleIntegrationSuite failure when SPARK_PREPEND_CLASSES set to 1

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:

18/02/13 07:33:29 INFO SparkContext: Starting job: collect at YarnShuffleIntegrationSuite.scala:143
Exception in thread "dag-scheduler-event-loop" java.lang.NoClassDefFoundError: breeze/linalg/DenseMatrix