关于Django项目启动报错RuntimeError: Model class wechat.models.UserInfo doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

写了一个django的项目，运行时出现如下错误： RuntimeError: Model class wechat.models.UserInfo doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.. 但之前这个model都没有改变过，网上查了半天没有结果 然后我将相应的UserInfo的引入行都删除，然后就正常了 ，分析可能是因为重复引入导致某些检查失败

方法二：在django的settings中的INSTALLED_APPS处添加'django.contrib.sites'进行app注册，并设置SITE_ID值。