title: celery parallel tasking error 'no result backend configured'
body: <p>Running django-celery 3.1.16, Celery 3.1.17, Django 1.4.16. Trying to run some parallel tasks using 3 workers and collect the results using the following:</p>
  
  <pre><code>from celery import group
  
  positions = []
  jobs = group(celery_calculate_something.s(data.id) for data in a_very_big_list)
  results = jobs.apply_async()
  positions.extend(results.get())
  </code></pre>
  
  <p>The task celery_calculate_something returns an object to place the in the results list:</p>
  
  <pre><code>app.task(ignore_result=False)
  def celery_calculate_something(id):
    &lt;do stuff&gt;
  </code></pre>
  
  <p>No matter what I try, I always get the same result when calling get() on results:</p>
  
  <pre><code>No result backend configured.  Please see the documentation for more information.
  </code></pre>
  
  <p>However, the results backend IS configured - I have many other tasks with ignore_result=False merrily adding to the tasks meta table in django_celery. It is something to do with using the results returned from group(). I should note it is not set explicitly in settings - it seems that django-celery has set it automatically for you.</p>
  
  <p>I have the worker collecting events using:</p>
  
  <pre><code>manage.py celery worker -l info -E
  </code></pre>
  
  <p>and celerycam running with </p>
  
  <pre><code>python manage.py celerycam
  </code></pre>
  
  <p>Inspecting the results object returned (an instance of GroupResult) I can see that the backend attr is an instance of DisabledBackend. Is this the problem? What have I mis-understood?</p>