title: Airflow scheduler unexpectedly shuts down
body: <p>I am running airflow <code>v1.8.0</code> on an EC2 instance with Ubuntu. The various DAGs that I have running connect with several different SQL tables. I've had a recurring issue where the scheduler, raised with <code>airflow scheduler -D</code> just shuts down on me. When I check <code>airflow-scheduler.err</code> there is no error. In order to debug I enter the <code>/airflow</code> directory and clear all scheduler-related files with <code>rm airflow-scheduler*</code> and restart the deamon. I am using <code>LocalExecutor</code>. </p>
  
  <p>Two questions: (1) What's going on and how can I fix it? (2) If there isn't a quick fix, is there at least a way for airflow to send me an email when the scheduler fails? </p>