This tests fails occasionally on mysql at least:

https://github.com/apache/airflow/pull/11555/checks?check_run_id=1260840314#step:9:1125

```
=================================== FAILURES ===================================
_____________ TestSchedulerJob.test_no_orphan_process_will_be_left _____________

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

    def test_no_orphan_process_will_be_left(self):
        empty_dir = mkdtemp()
        current_process = psutil.Process()
        old_children = current_process.children(recursive=True)
        scheduler = SchedulerJob(subdir=empty_dir,
                                 num_runs=1,
                                 executor=MockExecutor(do_update=False))
        scheduler.run()
        shutil.rmtree(empty_dir)
    
        # Remove potential noise created by previous tests.
        current_children = set(current_process.children(recursive=True)) - set(
            old_children)
>       self.assertFalse(current_children)
E       AssertionError: {psutil.Process(pid=3474, name='/usr/local/bin/', status='running', started='19:26:22')} is not false

tests/jobs/test_scheduler_job.py:871: AssertionError
```



tests/models/test_taskinstance.py
start_date = timezone.datetime(2016, 6, 1)
        dag = models.DAG(dag_id="test_handle_failure", schedule_interval=None, start_date=start_date)
        mock_on_failure_1 = mock.MagicMock()
        mock_on_retry_1 = mock.MagicMock()
        task1 = DummyOperator(
            task_id="test_handle_failure_on_failure",
            on_failure_callback=mock_on_failure_1,
            on_retry_callback=mock_on_retry_1,
            dag=dag,
        )
        ti1 = TI(task=task1, execution_date=start_date)
        ti1.state = State.FAILED
        ti1.handle_failure("test failure handling")
        ti1._run_finished_callback()
        context_arg_1 = mock_on_failure_1.call_args[0][0]
        assert context_arg_1 and "task_instance" in context_arg_1
        mock_on_retry_1.assert_not_called()
        mock_on_failure_2 = mock.MagicMock()
        mock_on_retry_2 = mock.MagicMock()
        task2 = DummyOperator(
            task_id="test_handle_failure_on_retry",