Completes this job exceptionally with a given exception. The result is
true if this job was completed as a result of this invocation and
false otherwise (if it was already completed). exception parameter is used as an additional debug information that is not handled by any exception handlers.
Subsequent invocations of this function have no effect and always produce
This function transitions this job into cancelled state if it was not completed or cancelled yet. However, that if this job has children, then it transitions into cancelling state and becomes cancelled once all its children are complete. See Job for details.