title: airflow: error: unrecognized arguments - Airflow scheduler error
body: <p>I created a DAG as follows :</p>
  
  <pre><code>args = {
      'owner': 'airflow',
      'start_date': datetime(2018, 12, 30),
      'retries': 5,
      'retry_delay': timedelta(minutes=30)
  }
  
  
  dag = DAG(
      dag_id='TEST',
      default_args=args,
      schedule_interval=timedelta(minutes=30),
      max_active_runs=1,
      catchup=False)
  
  task_op = DummyOperator(task_id='task', dag=dag)
  </code></pre>
  
  <p>saved it as <code>my_test.py</code> and uploaded it to the DAG folder.</p>
  
  <p>Started the DAG manually from the UI the DAG is queued but the task immediately fails. There is no log for the task but the scheduler log shows. </p>
  
  <pre><code>usage: airflow [-h]
                 {resetdb,render,variables,connections,pause,task_failed_deps,version,trigger_dag,initdb,test,unpause,dag_state,run,list_tasks,backfill,list_dags,kerberos,worker,webserver,flower,scheduler,task_state,pool,serve_logs,clear,upgradedb}
                 ...
  airflow: error: unrecognized arguments: my_test.py
  </code></pre>
  
  <p>I never encountered this before.  What is the problem?</p>
  
  <p>There is a similar question <a href="https://stackoverflow.com/questions/44184710/airflow-error-unrecognized-arguments-webserver">airflow: error: unrecognized arguments: webserver</a>  but it's totally different. The solution there is irrelevant here. </p>
  
  <p>Please advise what is the problem here</p>