Django model "doesn't declare an explicit app_label"

After a dozen hours of troubleshooting, I thought I was finally in business, but then I got:

Model class django.contrib.contenttypes.models.ContentType doesn't declare an explicit app_label 

There is so little info on this on the web, and no solution out there has resolved my issue.

I'm using Python 3.4 and Django 1.10.

From my settings.py:

INSTALLED_APPS = ['DeleteNote.apps.DeletenoteConfig','LibrarySync.apps.LibrarysyncConfig','django.contrib.admin','django.contrib.auth','django.contrib.contenttypes','django.contrib.sessions','django.contrib.messages','django.contrib.staticfiles',]

And my apps.py files look like this:

from django.apps import AppConfigclass DeletenoteConfig(AppConfig):    name = 'DeleteNote'

and

from django.apps import AppConfigclass LibrarysyncConfig(AppConfig):    name = 'LibrarySync'