Django 设置多环境配置文件载入问题

__init__.py
base.py
dev.py
prod.py

mysite/
 |-- mysite/
 | |-- __init__.py
 | |-- settings.py
 | |-- urls.py
 | +-- wsgi.py
 +-- manage.py

mysite/
 |-- mysite/
 | |-- __init__.py
 | |-- settings/  <-- 新建的文件夹
 | | |-- __init__.py <--
 | | |-- base.py <-- 旧的 settings.py
 | | |-- cli.py <-- 根据不同环境而新增的配置文件
 | | |-- dev.py
 | | +-- prod.py
 | |-- urls.py
 | +-- wsgi.py
 +-- manage.py

# settings/dev.py
from .base import *

DEBUG = True

INSTALLED_APPS += [
 'debug_toolbar',
]
...

python manage.py runserver --settings=mysite.settings.dev
python manage.py runserver --settings=mysite.settings.prod
python manage.py migrate --settings=mysite.settings.prod

# manage.py
import os
import sys
if __name__ == "__main__":
 os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings.dev") # 修改这个位置
 ...

import os
from django.core.wsgi import get_wsgi_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings.prod")
application = get_wsgi_application()

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(os.path.join(__file__, os.pardir))))

from .base import *
DEBUG = True
#其他配置

python manage.py runserver --settings=back-server.settings.dev