我在我的核心应用- www.example.com中调用此方法models.py，

from django.contrib.auth import get_user_model
User = get_user_model()

出现错误，

Exception has occurred: ImproperlyConfigured (note: full exception trace is shown but execution is paused at: <module>)
AUTH_USER_MODEL refers to model 'core.User' that has not been installed

调试器指向此行