Keyerror from celery task delay - django

Question

Following the celery getting started with Django instructions, I am able to run tasks, but not run the same task asynchronously using delay().
I added the following requirements to my Django project:
celery==4.3.0
redis==3.3.11
django-celery-results==1.1.2
psycopg2==2.7.3.1
django-cors-headers~=3.1.0
Created this celery.py in the pop_model project directory:
from __future__ import absolute_import, unicode_literals
import os
from celery import Celery
# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'pop_model.settings.local')
app = Celery('pop_model')
# namespace='CELERY' means all celery-related configuration keys
# should have a `CELERY_` prefix.
app.config_from_object('django.conf:settings', namespace='CELERY')
# Load task modules from all registered Django app configs.
app.autodiscover_tasks()
#app.task(bind=True)
def debug_task(self):
print('Request: {0!r}'.format(self.request))
Inserted this code in the project init.py:
from __future__ import absolute_import, unicode_literals
# This will make sure the app is always imported when
# Django starts so that shared_task will use this app.
from .celery import app as celery_app
__all__ = ('celery_app',)
Configured cors in the project settings and added these settings:
CELERY_BROKER_URL = 'redis://localhost:6379'
CELERY_RESULT_BACKEND = 'django-db' # defined in django_celery_results
CELERY_ACCEPT_CONTENT = ['json']
CELERY_RESULT_SERIALIZER = 'json'
CELERY_TASK_SERIALIZER = 'json'
I can start redis, then run celery using these commands:
export DJANGO_SETTINGS_MODULE=pop_model.settings.local
celery worker -A pop_model --loglevel=info
In a python3 shell, I get these results:
>>> from pop_model.celery import debug_task
>>> debug_task()
Request: <Context: {'args': (), 'kwargs': {}}>
>>> task=debug_task.delay()
Traceback (most recent call last):
File "/Users/janee/.virtualenvs/pop-model/lib/python3.6/site-packages/kombu/utils/objects.py", line 42, in __get__
return obj.__dict__[self.__name__]
KeyError: 'backend'
I don't know how to resolve the missing backend key as CELERY_RESULT_BACKEND is defined in the settings file.

Answer 1

The only difference between a normal Python shell and manage.py shell is that it exports your settings module (project_name.settings) in the DJANGO_SETTINGS_MODULE environment variable.
If you run the same interpreter with the proper environment variable you should see no change. Then, it may be that your pop_model.settings.local path is not returning a proper settings module for your app to latch on, or you're using a modified manage.py script (for development environment separation, I suppose) where the settings module is properly loaded.
You should be able to call your function using
./manage.py shell
from your project directory, using the same intepreter of your virtual environment. This could also work because the DJANGO_SETTINGS_MODULE needs a path that is present in the interpreter's search path (more on that here) and you could be calling the interpreter from another directory.