Critical Description
spark.yarn.user.classpath.first doesn't properly add the app jar to the system class path first. It has some logic there that i believe works for local files but running on yarn using distributed cache to distribute the app jar doesn't put _app_.jar into the classpath at all.
This is a break in backwards compatibility.
Note that in this case the user is trying to use different version of kryo (which used to work in spark 1.2) and the new configs for this: spark.
{driver, executor}.userClassPathFirst don't allow this as it errors out with:
User class threw exception: java.lang.LinkageError: loader constraint violation: loader (instance of org/apache/spark/util/ChildFirstURLClassLoader) previously initiated loading for a different type with name "com/esotericsoftware/kryo/Kryo"
