Checks to see if the job errored out.

def is_error(self):
        """ Checks to see if the job errored out. """
        try:
            if self._task.is_alive():
                if len(self._task.stderr.readlines()) > 0:
                    self._task.join()
                    self._write_log()
                    return True
        except AttributeError:
            pass
        return False