title: Celery server error: “cannot mix new setting names with old setting names”
body: <p>I am using celery server with redis as a broker and flask.</p>
  
  <p>After the flask server is running, I start the celery worker (by <code>celery -E -A app.celery worker</code>) but get the following error:</p>
  
  <pre><code>Process SpawnPoolWorker-115:
  Traceback (most recent call last):
    File "c:\users\a\appdata\local\programs\python\python36\lib\site-packages\kombu\utils\objects.py
      return obj.__dict__[self.__name__]
  KeyError: 'default_modules'
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "c:\users\a\appdata\local\programs\python\python36\lib\site-packages\kombu\utils\objects.py
      return obj.__dict__[self.__name__]
  KeyError: 'data'
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "c:\users\a\appdata\local\programs\python\python36\lib\site-packages\billiard\process.py",
      self.run()       [.....]
    File "c:\users\a\appdata\local\programs\python\python36\lib\site-packages\celery\app\utils.py",
      for key in sorted(really_left)
  celery.exceptions.ImproperlyConfigured:
  
  Cannot mix new setting names with old setting names, please
  rename the following settings to use the old format:
  
  include                              -&gt; CELERY_INCLUDE
  
  Or change all of the settings to use the new format :)
  </code></pre>
  
  <p>But I am not using the setting name <code>include</code> or <code>CELERY_INCLUDE</code> ...</p>
  
  <pre><code>celery = Celery(
      imports=app.import_name,
      result_backend=app.config['CELERY_RESULT_BACKEND'],
      broker_url=app.config['BROKER_URL']
  )
  </code></pre>
  
  <p>Where this error can come from?</p>