启动django 时，报错如下：

RuntimeError: Model class app.model.User.User doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

需要在 settings.py 中的INSTALLED_APPS 添加 app包名称

解决方案：

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    "app",
]

示意图