title: Celery does not registering tasks
body: <p>
  Hello! I just started to use Celery with Django. I've a task that i need to be periodic. In admin interface I can see my task in dropdown list named "Task (registered):". But when Celery Beat tries to execute it NotRegistered exception is thrown.</p>
  
  <p>Python 3.5.2, Django 1.11.4, Celery 4.1, django-celery-beat 1.1.0, django-celery-results 1.0.1</p>
  
  <p>
  Part of settings.py related to celery:</p>
  
  <pre><code>CELERY_BROKER_URL = 'amqp://user:*****@192.168.X.X/proj'
  CELERY_ACCEPT_CONTENT = ['json']
  CELERY_RESULT_BACKEND = 'django-db'
  CELERY_TASK_SERIALIZER = 'json'
  CELERY_RESULT_SERIALIZER = 'json'
  CELERY_TIMEZONE = 'Europe/Moscow'
  </code></pre>
  
  <p>celery.py and proj/__init__.py are identical to documentation examples.</p>
  
  <p>proj/celery.py:</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', 'proj.settings')
  
  app = Celery('proj')
  
  app.config_from_object(settings, namespace='CELERY')
  
  app.autodiscover_tasks()
  
  @app.task(bind=True)
  def debug_task(self):
      print('Request: {0!r}'.format(self.request))
  </code></pre>
  
  <p>proj/__init__.py:</p>
  
  <pre><code>from __future__ import absolute_import, unicode_literals
  from .celery import app as celery_app
  
  __all__ = ['celery_app']
  </code></pre>
  
  <p>tasks.py:</p>
  
  <pre><code>from celery import shared_task
  from core.backend.files import SFTP
  
  @shared_task
  def load_files_from_sftp():
      ftp = SFTP()
      ftp.get_files()
  </code></pre>
  
  <p>I get the following json result: 
  {"exc_message": "'core.tasks.load_files_from_sftp'", "exc_type": "NotRegistered"}</p>
  
  <p>If I try to use celery.task.control.inspect() from shell, it is only debug_task() there. Just stuck! ( I'll be grateful for any help.</p>