Update Jan 2022: This answer is outdated. As suggested in comments, please refer to this link
The problem is that you are trying to connect to a local instance of RabbitMQ. Look at this line in your settings.py
BROKER_URL = 'amqp://guest:guest@localhost:5672/'
If you are working currently on development, you could avoid setting up Rabbit and all the mess around it, and just use a development version of a message queue with the Django database.
Do this by replacing your previous configuration with:
BROKER_URL = 'django://'
…and add this app:
INSTALLED_APPS += ('kombu.transport.django', )
Finally, launch the worker with:
./manage.py celery worker --loglevel=info
Source: http://docs.celeryproject.org/en/latest/getting-started/brokers/django.html