Commit in master/v1-9-test breaks Airflow scheduler from scheduling DAGs

[David Klosowski]

Hey Airflow Devs:

The following commit for, AIRFLOW-1641, recently added breaks the scheduler
in Airflow

Master:
https://github.com/apache/incubator-airflow/commit/2abead7049806482047e29d123a109b444c00355

v1-9-test:
https://github.com/apache/incubator-airflow/commit/73549763eac74142b7c4018422bb2f8c897b45a8

No tasks ever get scheduled by the scheduler.  Please advise.

Thanks.

Regards,
David