python django runserver时报错 django.core.exceptions.AppRegistryNotReady:Apps aren't loaded yet. 求解！！

F:\2019综合课程设计\参考源码0105\mis>python manage.py runserver
Traceback (most recent call last):
  File "manage.py", line 5, in 
    django.setup()
  File "E:\Python\lib\site-packages\django\__init__.py", line 19, in setup
    configure_logging(settings.LOGGING_CONFIG, settings.LOGGING)
  File "E:\Python\lib\site-packages\django\conf\__init__.py", line 57, in __getattr__
    self._setup(name)
  File "E:\Python\lib\site-packages\django\conf\__init__.py", line 44, in _setup
    self._wrapped = Settings(settings_module)
  File "E:\Python\lib\site-packages\django\conf\__init__.py", line 107, in __init__
    mod = importlib.import_module(self.SETTINGS_MODULE)
  File "E:\Python\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "", line 1006, in _gcd_import
  File "", line 983, in _find_and_load
  File "", line 953, in _find_and_load_unlocked
  File "", line 219, in _call_with_frames_removed
  File "", line 1006, in _gcd_import
  File "", line 983, in _find_and_load
  File "", line 967, in _find_and_load_unlocked
  File "", line 677, in _load_unlocked
  File "", line 728, in exec_module
  File "", line 219, in _call_with_frames_removed
  File "F:\2019综合课程设计\参考源码0105\mis\mis\__init__.py", line 8, in 
    admin.site.site_header = 'Django-ERP'
  File "E:\Python\lib\site-packages\django\utils\functional.py", line 244, in __setattr__
    self._setup()
  File "E:\Python\lib\site-packages\django\contrib\admin\sites.py", line 526, in _setup
    AdminSiteClass = import_string(apps.get_app_config('admin').default_site)
  File "E:\Python\lib\site-packages\django\apps\registry.py", line 150, in get_app_config
    self.check_apps_ready()
  File "E:\Python\lib\site-packages\django\apps\registry.py", line 132, in check_apps_ready
    raise AppRegistryNotReady("Apps aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

manage.py:

#!/usr/bin/env python
import os
import django
import sys

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mis.settings")
django.setup()

from django.core.management import execute_from_command_line
execute_from_command_line(sys.argv)