code: public Throwable getError(ClassLoader userCodeClassloader) {
  		if (this.throwable == null) {
  			return null;
  		}
  		else {
  			return this.throwable.deserializeError(userCodeClassloader);
  		}
  	}
docs: Gets the attached exception, which is in serialized form. Returns null,
  if the status update is no failure with an associated exception.
  
  @param userCodeClassloader The classloader that can resolve user-defined exceptions.
  @return The attached exception, or null, if none.