Log failure of a step

def _step_failure(self, exc):
        """ Log failure of a step """
        self.log_crit(u"STEP %d (%s) FAILURE" % (self.step_index, self.step_label))
        self.step_index += 1
        self.log_exc(u"Unexpected error while executing task", exc, True, ExecuteTaskExecutionError)