title: Airflow: Celery task failure
body: <p>I have airflow up and running but I have an issue where my task is failing in celery.</p>
  
  <pre><code>Traceback (most recent call last):
    File "/usr/local/lib/python3.6/site-packages/airflow/executors/celery_executor.py", line 52, in execute_command
      subprocess.check_call(command, shell=True)
    File "/usr/local/lib/python3.6/subprocess.py", line 291, in check_call
      raise CalledProcessError(retcode, cmd)
  subprocess.CalledProcessError: Command 'airflow run airflow_tutorial_v01 print_hello 2017-06-01T15:00:00 --local -sd /usr/local/airflow/dags/hello_world.py' returned non-zero exit status 1.
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/usr/local/lib/python3.6/site-packages/celery/app/trace.py", line 375, in trace_task
      R = retval = fun(*args, **kwargs)
    File "/usr/local/lib/python3.6/site-packages/celery/app/trace.py", line 632, in __protected_call__
      return self.run(*args, **kwargs)
    File "/usr/local/lib/python3.6/site-packages/airflow/executors/celery_executor.py", line 55, in execute_command
      raise AirflowException('Celery command failed')
  airflow.exceptions.AirflowException: Celery command failed
  </code></pre>
  
  <p>it is a very basic DAG (taken from the hello world tutorial: <a href="https://github.com/apache/incubator-airflow/blob/master/airflow/example_dags/tutorial.py" rel="nofollow noreferrer">https://github.com/apache/incubator-airflow/blob/master/airflow/example_dags/tutorial.py</a>).</p>
  
  <p>Also I do not see any logs of my worker, I got this stack strace from the Flower web interface.</p>
  
  <p>If I run manually on the worker node, the airflow run command mentionned in the stack trace it works.
  How can I get more information to debug further?</p>
  
  <pre><code>The only log I get when starting `airflow work` is
  root@ip-10-0-4-85:~# /usr/local/lib/python3.5/dist-packages/psycopg2/__init__.py:144: UserWarning: The psycopg2 wheel package will be renamed from release 2.8; in order to keep installing from binary please use "pip install psycopg2-binary" instead. For details see: &lt;http://initd.org/psycopg/docs/install.html#binary-install-from-pypi&gt;.
    """)
  [2018-07-25 17:49:43,430] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python3.5/lib2to3/Grammar.txt
  [2018-07-25 17:49:43,469] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python3.5/lib2to3/PatternGrammar.txt
  [2018-07-25 17:49:43,594] {__init__.py:45} INFO - Using executor CeleryExecutor
  Starting flask
  [2018-07-25 17:49:43,665] {_internal.py:88} INFO -  * Running on http://0.0.0.0:8793/ (Press CTRL+C to quit)
  ^C
  </code></pre>
  
  <p>The config I use is the default one with a postgresql and redis backend for celery.
  I see the worked online in Flower.</p>
  
  <p>Thanks.</p>
  
  <p>edit: edited for more informations</p>