CELERY_ALWAYS_EAGER seems to have no effect - django

Question

I have a Django + Celery setup working correctly in production with RabbitMQ.
AFAIK, it should be sufficient to set CELERY_ALWAYS_EAGER to True in django settings locally, to avoid setting up RabbitMQ for development. I have done this but when calling .delay() on a task I get:
Traceback (most recent call last):
File "lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "lib/python2.7/site-packages/django/views/generic/base.py", line 71, in view
return self.dispatch(request, *args, **kwargs)
File "lib/python2.7/site-packages/django/views/generic/base.py", line 89, in dispatch
return handler(request, *args, **kwargs)
File "lib/python2.7/site-packages/django/views/generic/edit.py", line 215, in post
return self.form_valid(form)
File "app/web/views.py", line 188, in form_valid
form.send_email()
File "app/web/forms.py", line 17, in send_email
send_email.delay(mail, recipients, 'Contact %s' % name, comment)
File "lib/python2.7/site-packages/celery/app/task.py", line 453, in delay
return self.apply_async(args, kwargs)
File "lib/python2.7/site-packages/celery/app/task.py", line 559, in apply_async
**dict(self._get_exec_options(), **options)
File "lib/python2.7/site-packages/celery/app/base.py", line 353, in send_task
reply_to=reply_to or self.oid, **options
File "lib/python2.7/site-packages/celery/app/amqp.py", line 305, in publish_task
**kwargs
File "lib/python2.7/site-packages/kombu/messaging.py", line 172, in publish
routing_key, mandatory, immediate, exchange, declare)
File "lib/python2.7/site-packages/kombu/connection.py", line 457, in _ensured
interval_max)
File "lib/python2.7/site-packages/kombu/connection.py", line 369, in ensure_connection
interval_start, interval_step, interval_max, callback)
File "lib/python2.7/site-packages/kombu/utils/__init__.py", line 243, in retry_over_time
return fun(*args, **kwargs)
File "lib/python2.7/site-packages/kombu/connection.py", line 237, in connect
return self.connection
File "lib/python2.7/site-packages/kombu/connection.py", line 741, in connection
self._connection = self._establish_connection()
File "lib/python2.7/site-packages/kombu/connection.py", line 696, in _establish_connection
conn = self.transport.establish_connection()
File "lib/python2.7/site-packages/kombu/transport/librabbitmq.py", line 123, in establish_connection
conn = self.Connection(**opts)
File "lib/python2.7/site-packages/librabbitmq/__init__.py", line 199, in __init__
self.connect()
ConnectionError: Error opening socket: a socket error occurred

Answer 1

For the record, since celery 4.0 this setting has been renamed to task_always_eager:
# setting renamed on celery 4.0
CELERY_ALWAYS_EAGER --> task_always_eager
To help the migration to this version, Celery provides the following util to update automatically your settings:
# --django allows to keep uppercase settings and CELERY_ prefix
$ celery upgrade settings proj/settings.py --django

Answer 2

So I have found the problem. Basically I was missing:
from .celery import app as celery_app
in proj/proj/__init__.py
For some misterious reason this seems to fail only when running runserver and not when running wsgi.py via uWSGI. Not sure why, but with the import it works on runserver too.