I went through this example here:
http://docs.celeryproject.org/en/latest/django/first-steps-with-django.html
All my tasks are in files called tasks.py.
Did you add the line:
from __future__ import absolute_import
to the top of your cloud/celery.py module?
cloud/celery.py
Read the breakdown of the example here: http://docs.celeryproject.org/en/latest/django/first-steps-with-django.html