We have flaky scheduler test:


https://github.com/apache/airflow/pull/11659/checks?check_run_id=1279791496#step:6:527


_______________ TestSchedulerJob.test_scheduler_task_start_date ________________

self = <tests.jobs.test_scheduler_job.TestSchedulerJob testMethod=test_scheduler_task_start_date>

    def test_scheduler_task_start_date(self):
        """
        Test that the scheduler respects task start dates that are different from DAG start dates
        """
    
        dagbag = DagBag(dag_folder=os.path.join(settings.DAGS_FOLDER, "no_dags.py"), include_examples=False)
        dag_id = 'test_task_start_date_scheduling'
        dag = self.dagbag.get_dag(dag_id)
        dag.is_paused_upon_creation = False
        dagbag.bag_dag(dag=dag, root_dag=dag)
    
        # Deactivate other dags in this file so the scheduler doesn't waste time processing them
        other_dag = self.dagbag.get_dag('test_start_date_scheduling')
        other_dag.is_paused_upon_creation = True
        dagbag.bag_dag(dag=other_dag, root_dag=other_dag)
    
        dagbag.sync_to_db()
    
        scheduler = SchedulerJob(executor=self.null_exec,
                                 subdir=dag.fileloc,
                                 num_runs=2)
        scheduler.run()
    
        session = settings.Session()
        tiq = session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id)
        ti1s = tiq.filter(TaskInstance.task_id == 'dummy1').all()
        ti2s = tiq.filter(TaskInstance.task_id == 'dummy2').all()
        self.assertEqual(len(ti1s), 0)
>       self.assertEqual(len(ti2s), 2)
E       AssertionError: 1 != 2
tests/models/test_taskinstance.py
self,
        trigger_rule,
        successes,
        skipped,
        failed,
        upstream_failed,
        done,
        flag_upstream_failed,
        expect_state,
        expect_completed,
    ):
        start_date = timezone.datetime(2016, 2, 1, 0, 0, 0)
        dag = models.DAG('test-dag', start_date=start_date)
        downstream = DummyOperator(task_id='downstream', dag=dag, owner='airflow', trigger_rule=trigger_rule)
        for i in range(5):
            task = DummyOperator(task_id=f'runme_{i}', dag=dag, owner='airflow')
            task.set_downstream(downstream)
        run_date = task.start_date + datetime.timedelta(days=5)
        ti = TI(downstream, run_date)
        dep_results = TriggerRuleDep()._evaluate_trigger_rule(  
            ti=ti,
            successes=successes,
            skipped=skipped,
            failed=failed,
            upstream_failed=upstream_failed,