Stops trial.

        Trials may be stopped at any time. If trial is in state PENDING
        or PAUSED, calls `on_trial_remove`  for scheduler and
        `on_trial_complete(..., early_terminated=True) for search_alg.
        Otherwise waits for result for the trial and calls
        `on_trial_complete` for scheduler and search_alg if RUNNING.

def stop_trial(self, trial):
        """Stops trial.

        Trials may be stopped at any time. If trial is in state PENDING
        or PAUSED, calls `on_trial_remove`  for scheduler and
        `on_trial_complete(..., early_terminated=True) for search_alg.
        Otherwise waits for result for the trial and calls
        `on_trial_complete` for scheduler and search_alg if RUNNING.
        """
        error = False
        error_msg = None

        if trial.status in [Trial.ERROR, Trial.TERMINATED]:
            return
        elif trial.status in [Trial.PENDING, Trial.PAUSED]:
            self._scheduler_alg.on_trial_remove(self, trial)
            self._search_alg.on_trial_complete(
                trial.trial_id, early_terminated=True)
        elif trial.status is Trial.RUNNING:
            try:
                result = self.trial_executor.fetch_result(trial)
                trial.update_last_result(result, terminate=True)
                self._scheduler_alg.on_trial_complete(self, trial, result)
                self._search_alg.on_trial_complete(
                    trial.trial_id, result=result)
            except Exception:
                error_msg = traceback.format_exc()
                logger.exception("Error processing event.")
                self._scheduler_alg.on_trial_error(self, trial)
                self._search_alg.on_trial_complete(trial.trial_id, error=True)
                error = True

        self.trial_executor.stop_trial(trial, error=error, error_msg=error_msg)