### Body

Add unit test for changes in https://github.com/apache/airflow/pull/17305

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
tests/jobs/test_backfill_job.py
mock_log.debug,
            NoAvailablePoolSlot,
        )
        times_task_concurrency_limit_reached_in_debug = self._times_called_with(
            mock_log.debug,
            TaskConcurrencyLimitReached,
        )
        assert 0 == times_dag_concurrency_limit_reached_in_debug
        assert 0 == times_task_concurrency_limit_reached_in_debug
        assert times_pool_limit_reached_in_debug > 0
    def test_backfill_pool_not_found(self, dag_maker):
        dag = self._get_dummy_dag(
            dag_maker,
            dag_id='test_backfill_pool_not_found',
            pool='king_pool',
        )
        dag_maker.create_dagrun()
        executor = MockExecutor()
        job = BackfillJob(
            dag=dag,
            executor=executor,
            start_date=DEFAULT_DATE,
            end_date=DEFAULT_DATE + datetime.timedelta(days=7),
        )
        try:
            job.run()
        except AirflowException:
            return
    @patch('airflow.jobs.backfill_job.BackfillJob.log')
    def test_backfill_respect_pool_limit(self, mock_log, dag_maker):