AppRegistryNotReady: Models aren't loaded yet.

objects.all().delete()でエラー

    C:\Users\shohaya\tf-manager\tfmanager\db>python initteam.py
Traceback (most recent call last):
  File "initteam.py", line 60, in 
    init_team()
  File "initteam.py", line 49, in init_team
    obj.delete()
  File "C:\Anaconda\lib\site-packages\django\db\models\base.py", line 740, in de
lete
    collector.collect([self])
  File "C:\Anaconda\lib\site-packages\django\db\models\deletion.py", line 191, i
n collect
    include_hidden=True, include_proxy_eq=True):
  File "C:\Anaconda\lib\site-packages\django\db\models\options.py", line 498, in
 get_all_related_objects
    include_proxy_eq=include_proxy_eq)]
  File "C:\Anaconda\lib\site-packages\django\db\models\options.py", line 510, in
 get_all_related_objects_with_model
    self._fill_related_objects_cache()
  File "C:\Anaconda\lib\site-packages\django\db\models\options.py", line 533, in
 _fill_related_objects_cache
    for klass in self.apps.get_models(include_auto_created=True):
  File "C:\Anaconda\lib\site-packages\django\utils\lru_cache.py", line 101, in w
rapper
    result = user_function(*args, **kwds)
  File "C:\Anaconda\lib\site-packages\django\apps\registry.py", line 168, in get
_models
    self.check_models_ready()
  File "C:\Anaconda\lib\site-packages\django\apps\registry.py", line 131, in che
ck_models_ready
    raise AppRegistryNotReady("Models aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

コードの最初に

    import django
    django.setup()

とすると直った。なんでかは分からない

    http://stackoverflow.com/questions/27021707/django-filtering-querysets-causes-appregistrynotready-models-arent-loaded-yet
    http://stackoverflow.com/questions/25939719/django-ver-1-7-appregistrynotready-models-arent-loaded-yet
    http://djangotalk.blogspot.jp/2014/09/re-appregistrynotready-models-arent_25.html