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/jobs/test_scheduler_job.py
dags_folder = mkdtemp()
        try:
            invalid_zip_filename = os.path.join(dags_folder, "test_zip_invalid.zip")
            invalid_dag_filename = os.path.join(dags_folder, "test_zip_invalid.zip", TEMP_DAG_FILENAME)
            with ZipFile(invalid_zip_filename, "w") as invalid_zip_file:
                invalid_zip_file.writestr(TEMP_DAG_FILENAME, INVALID_DAG_WITH_DEPTH_FILE_CONTENTS)
            self.run_single_scheduler_loop_with_no_dags(dags_folder)
        finally:
            shutil.rmtree(dags_folder)
        with create_session() as session:
            import_errors = session.query(errors.ImportError).all()
        assert len(import_errors) == 1
        import_error = import_errors[0]
        assert import_error.filename == invalid_zip_filename
        expected_stacktrace = (
            "Traceback (most recent call last):\n"
            '  File "{}", line 2, in something\n'
            "    return airflow_DAG\n"
            "NameError: name 'airflow_DAG' is not defined\n"
        )
        assert import_error.stacktrace == expected_stacktrace.format(invalid_dag_filename)
    def test_list_py_file_paths(self):