This is not exactly a new problem, but may be exacerbated here. Could this new-fangled way of returning output instead of a classpath in error conditions result in bad things happening here:
https://github.com/apache/spark/blob/5af99d7617ba3b9fbfdb345ef9571b7dd41f45a1/core/src/main/scala/org/apache/spark/deploy/worker/CommandUtils.scala#L72
?