Silence 90% of remaining Django 1.8 model warnings.

mayan/apps/document_comments/apps.py

@@ -1,10 +1,10 @@
 from __future__ import unicode_literals
 
+from django.apps import apps
 from django.utils.translation import ugettext_lazy as _
 
 from acls import ModelPermission
 from common import MayanAppConfig, menu_facet, menu_object, menu_sidebar
-from documents.models import Document
 from navigation import SourceColumn
 
 from .links import (
@@ -25,6 +25,10 @@ class DocumentCommentsApp(MayanAppConfig):
     def ready(self):
         super(DocumentCommentsApp, self).ready()
 
+        Document = apps.get_model(
+            app_label='documents', model_name='Document'
+        )
+
         Comment = self.get_model('Comment')
 
         ModelPermission.register(