Django channels实现websocket时，报错django.core.exceptions.ImproperlyConfigured: Cannot import ASGI_APPLIC

Django项目使用channels实现websocket时，

项目文件：mysite/asgi.py

import os
import django
from django.core.asgi import get_asgi_application

from channels.routing import ProtocolTypeRouter, URLRouter
from channels.auth import AuthMiddlewareStack  
from socketServer import routing

os.environ.setdefault