title: Celery run error
body: <p>I made a Celery app according to a tutorial in this <a href="https://www.digitalocean.com/community/tutorials/how-to-use-celery-with-rabbitmq-to-queue-tasks-on-an-ubuntu-vps" rel="nofollow noreferrer">link</a>, but I just some errors. After googling I downgraded to Celery version 3.1.25, <a href="https://stackoverflow.com/a/40795761/4838661">claimed to be the last version supporting windows</a>. But the errors I get remain the same.
  What is the problem?</p>
  
  <pre><code># tasks.py
  from celery import Celery
  
  app = Celery('tasks', backend='amqp', broker='amqp://')
  
  @app.task
  def add(x, y):
      return x + y
  
  @app.task(ignore_result=True)
  def print_hello():
      print('hello there')
  
  @app.task
  def gen_prime(x):
      multiples = []
      results = []
      for i in range(2, x+1):
          if i not in multiples:
              results.append(i)
              for j in range(i*i, x+1, i):
                  multiples.append(j)
      return results
  </code></pre>
  
  <p>The error message I get on celery running command prompt:</p>
  
  <pre><code>C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  
  -------------- celery@pc v4.2.1 (windowlicker)
  ---- **** -----
  --- * ***  * -- Windows-10-10.0.17134-SP0 2018-1-28 08:19:41
  -- * - **** ---
  - ** ---------- [config]
  - ** ---------- .&gt; app:         tasks:0x262e454cba8
  - ** ---------- .&gt; transport:   amqp://guest:**@localhost:5672//
  - ** ---------- .&gt; results:     amqp://
  - *** --- * --- .&gt; concurrency: 8 (prefork)
  -- ******* ---- .&gt; task events: ON
  --- ***** -----
  -------------- [queues]
                  .&gt; celery           exchange=celery(direct) key=celery
  
  
  [tasks]
  . tasks.add
  . tasks.gen_prime
  . tasks.print_hello
  
  [2018-1-28 08:19:41,369: INFO/MainProcess] Connected to amqp://guest:**@127.0.0.1:5672//
  [2018-1-28 08:19:41,490: INFO/MainProcess] mingle: searching for neighbors
  [2018-1-28 08:19:42,676: INFO/SpawnPoolWorker-5] child process 5904 calling self.run()
  [2018-1-28 08:19:42,685: INFO/SpawnPoolWorker-1] child process 15432 calling self.run()
  [2018-1-28 08:19:42,688: WARNING/SpawnPoolWorker-5] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,690: INFO/SpawnPoolWorker-3] child process 9580 calling self.run()
  [2018-1-28 08:19:42,697: WARNING/SpawnPoolWorker-1] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,700: INFO/SpawnPoolWorker-2] child process 15660 calling self.run()
  [2018-1-28 08:19:42,703: WARNING/SpawnPoolWorker-3] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,710: WARNING/SpawnPoolWorker-2] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,724: INFO/SpawnPoolWorker-7] child process 2612 calling self.run()
  [2018-1-28 08:19:42,724: INFO/SpawnPoolWorker-6] child process 15192 calling self.run()
  [2018-1-28 08:19:42,725: INFO/SpawnPoolWorker-4] child process 5276 calling self.run()
  [2018-1-28 08:19:42,731: INFO/SpawnPoolWorker-8] child process 16112 calling self.run()
  [2018-1-28 08:19:42,733: WARNING/SpawnPoolWorker-6] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  [2018-1-28 08:19:42,733: WARNING/SpawnPoolWorker-7] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')    The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.     Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  
  [2018-1-28 08:19:42,734: WARNING/SpawnPoolWorker-4] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,739: WARNING/SpawnPoolWorker-8] C:\Python3\lib\site-packages\celery\backends\amqp.py:67: CPendingDeprecationWarning:
      The AMQP result backend is scheduled for deprecation in     version 4.0 and removal in version v5.0.
  Please use RPC backend or a persistent backend.
  
  alternative='Please use RPC backend or a persistent backend.')
  [2018-1-28 08:19:42,792: INFO/MainProcess] mingle: all alone
  [2018-1-28 08:19:42,802: INFO/MainProcess] celery@sh-int24 ready.
  [2018-1-28 20:00:12,625: INFO/MainProcess] Received task: tasks.gen_prime[d293687a-c032-47e4-b9b2-4097a448d5e7]
  [2018-1-28 20:00:12,688: ERROR/MainProcess] Task handler raised error: ValueError('not enough values to unpack (expected 3, got 0)',)
  Traceback (most recent call last):
  File "C:\Python3\lib\site-packages\billiard\pool.py", line 358, in workloop
      result = (True, prepare_result(fun(*args, **kwargs)))
  File "C:\Python3\lib\site-packages\celery\app\trace.py", line 537, in _fast_trace_task
      tasks, accept, hostname = _loc
  ValueError: not enough values to unpack (expected 3, got 0)
  </code></pre>
  
  <p>And the command I issue:
  <code>celery -A tasks worker</code></p>
  
  <p>I use Windows 10 and python 3.6 anaconda distribution.</p>