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
task = DummyOperator(task_id='op')
        ti = TI(task=task, execution_date=datetime.datetime.now())
        params = {"override": False}
        dag_run = DagRun()
        ti.overwrite_params_with_dag_run_conf(params, dag_run)
        assert params["override"] is False
    @patch('airflow.models.taskinstance.send_email')
    def test_email_alert(self, mock_send_email):
        dag = models.DAG(dag_id='test_failure_email')
        task = BashOperator(
            task_id='test_email_alert', dag=dag, bash_command='exit 1', start_date=DEFAULT_DATE, email='to'
        )
        ti = TI(task=task, execution_date=timezone.utcnow())
        try:
            ti.run()
        except AirflowException:
            pass
        (email, title, body), _ = mock_send_email.call_args
        assert email == 'to'
        assert 'test_email_alert' in title
        assert 'test_email_alert' in body
        assert 'Try 1' in body
    @conf_vars(
        {
            ('email', 'subject_template'): '/subject/path',
            ('email', 'html_content_template'): '/html_content/path',
        }
    )
    @patch('airflow.models.taskinstance.send_email')
    def test_email_alert_with_config(self, mock_send_email):