title: django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet. with celery beat
body: <p>I have a periodic task which creates and saves model every second. So i configured this</p>
  
  <pre><code>CELERY_IMPORTS = (
      'myapp.tasks',
  )
  
  CELERY_BEAT_SCHEDULE = {
      'periodic_task': {
          'task': 'myapp.tasks.periodic_task',
          'schedule': timedelta(seconds=1),
      },
  }
  </code></pre>
  
  <p>and typical <em>celery.py</em>:</p>
  
  <pre><code>from __future__ import absolute_import, unicode_literals
  import os
  from celery import Celery
  from django.conf import settings
  
  os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myapp.settings')
  
  app = Celery('myapp')
  app.config_from_object('django.conf:settings', namespace='CELERY')
  app.autodiscover_tasks()
  
  @app.task(bind=True)
  def debug_task(self):
      print('Request: {0!r}'.format(self.request))
  </code></pre>
  
  <p>and finally i've configured <strong>supervisord</strong> to start this:</p>
  
  <pre><code>[program:myapp-celery]
  command=/home/me/myapp/venv/bin/celery worker -A myapp --loglevel=INFO
  directory=/home/me/myapp
  user=nobody
  numprocs=1
  stdout_logfile=/home/me/myapp/logs/celery.log
  stderr_logfile=/home/me/myapp/logs/celery.log
  autostart=true
  autorestart=true
  startsecs=10
  
  stopwaitsecs = 600
  stopasgroup=true
  priority=1000
  </code></pre>
  
  <p>And it starts function in <strong>tasks.py</strong> which uses imported model, which as i understand is not loaded yet, causing this error</p>
  
  <pre><code>django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.&gt;
  </code></pre>
  
  <p>So i want some hook or flag indicating that everything is set so that my schedule can start executing this periodically.</p>