问题 I am deploying a Django 1.10 project onto an Ubuntu server with Apache and mod_wsgi. I am getting the following 500 error which I can't solve: RuntimeError: Model class django.contrib.contenttypes.models.ContentType doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS. installed_apps in settings.py: INSTALLED_APPS = [ 'django.contrib.sites', 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib