Use app registry instead of INSTALLED_APPS to discover celery tasks (#754)

* Use app registry instead of INSTALLED_APPS to discover celery tasks. Fixes #717

* Added Daniel Hepper to contributors list

CONTRIBUTORS.rst

@@ -70,6 +70,7 @@ Listed in alphabetical order.
   Cristian Vargas          `@cdvv7788`_
   Cullen Rhodes            `@c-rhodes`_
   Dan Shultz               `@shultz`_
+  Daniel Hepper            `@dhepper`_                   @danielhepper
   Daniele Tricoli          `@eriol`_
   David Díaz               `@ddiazpinto`_                @DavidDiazPinto
   Davur Clementsen         `@dsclementsen`_              @davur
@@ -158,6 +159,7 @@ Listed in alphabetical order.
 .. _@Collederas: https://github.com/Collederas
 .. _@ddiazpinto: https://github.com/ddiazpinto
 .. _@dezoito: https://github.com/dezoito
+.. _@dhepper: https://github.com/dhepper
 .. _@dot2dotseurat: https://github.com/dot2dotseurat
 .. _@dsclementsen: https://github.com/dsclementsen
 .. _@epileptic-fish: https://gihub.com/epileptic-fish

{{cookiecutter.project_slug}}/{{cookiecutter.project_slug}}/taskapp/celery.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import
 import os
 from celery import Celery
-from django.apps import AppConfig
+from django.apps import apps, AppConfig
 from django.conf import settings
 
 
@@ -22,7 +22,8 @@ class CeleryConfig(AppConfig):
         # Using a string here means the worker will not have to
         # pickle the object when using Windows.
         app.config_from_object('django.conf:settings')
-        app.autodiscover_tasks(lambda: settings.INSTALLED_APPS, force=True)
+        installed_apps = [app_config.name for app_config in apps.get_app_configs()]
+        app.autodiscover_tasks(lambda: installed_apps, force=True)
 
         {% if cookiecutter.use_sentry_for_error_reporting == 'y' -%}
         if hasattr(settings, 'RAVEN_CONFIG'):