无法将 Django 从 1.7 迁移到 1.8

问：

将 django 1.7 升级到 1.8 时（最终目标是将 1.4 迁移到 1.11LTS） 我被要求从我的INSTALLED_APPS中删除 SOUTH

很好，但后来我得到：

raise AppRegistryNotReady("Models aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet. 

所以我尝试添加设置文件：

import django
django.setup()

但它在运行时带来了这个错误，这让我认为这不是正确的方式：

AUTH_USER_MODEL refers to model 'auth.User' that has not been installed

我的INSTALLED_APPS：

'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.staticfiles',
'mptt',
# 'south',
'main',
'proxy',
'picocms',
'django.contrib.admin',
'reports',
'django_orphaned'

请注意，如果我注释“main”（我的主代码文件夹）和“picocms”（一个过时的库），则不会再引发 AppRegistryNotReady 异常（但显然没有它，项目就无法工作）

有人成功经历过同样的问题吗？

stackTrace（获取信息）

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/core/management/__init__.py", line 312, in execute
    django.setup()
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/apps/config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/local/Cellar/python@2/2.7.15_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File ".../workspace/django/cms/main/models.py", line 19, in <module>
    from picocms.models import CMSModel, CMSCategory, ActiveModelManager, PublicModelManager
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/picocms/models.py", line 13, in <module>
    class CMSCategory(MPTTModel):
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/mptt/models.py", line 189, in __new__
    return meta.register(cls)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/mptt/models.py", line 273, in register
    manager.init_from_model(cls)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/mptt/managers.py", line 58, in init_from_model
    [tree_field] = [fld for fld in model._meta.get_fields_with_model() if fld[0].name == self.tree_id_attr]
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 56, in wrapper
    return fn(*args, **kwargs)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 432, in get_fields_with_model
    return [self._map_model(f) for f in self.get_fields()]
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 740, in get_fields
    return self._get_fields(include_parents=include_parents, include_hidden=include_hidden)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 802, in _get_fields
    all_fields = self._relation_tree
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/utils/functional.py", line 60, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 709, in _relation_tree
    return self._populate_directed_relation_graph()
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/db/models/options.py", line 681, in _populate_directed_relation_graph
    all_models = self.apps.get_models(include_auto_created=True)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/utils/lru_cache.py", line 101, in wrapper
    result = user_function(*args, **kwds)
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/apps/registry.py", line 168, in get_models
    self.check_models_ready()
  File ".../.virtualenvs/migre/lib/python2.7/site-packages/django/apps/registry.py", line 131, in check_models_ready
    raise AppRegistryNotReady("Models aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.