Change celery tasks to shared task decorator

tests/__init__.py

@@ -0,0 +1,3 @@
+from .celery import app as celery_app
+
+__all__ = ['celery_app']

tests/celery.py

@@ -0,0 +1,16 @@
+import os, sys
+from celery import Celery
+
+# set the default Django settings module for the 'celery' program.
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'settings')
+
+from django.conf import settings  # noqa
+
+app = Celery('devauth')
+
+# Using a string here means the worker don't have to serialize
+# the configuration object to child processes.
+app.config_from_object('django.conf:settings')
+
+# Load task modules from all registered Django app configs.
+app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)