Fixed a bad filter argument found by the Django 1.8 code.

 - Legacy-Id: 12408

Author: levkowetz

ietf/doc/models.py

@@ -277,7 +277,7 @@ def relations_that(self, relationship):
         if isinstance(self, Document):
             return RelatedDocument.objects.filter(target__document=self, relationship__in=relationship).select_related('source')
         elif isinstance(self, DocHistory):
-            return RelatedDocHistory.objects.filter(target__document=self, relationship__in=relationship).select_related('source')
+            return RelatedDocHistory.objects.filter(target__document=self.doc, relationship__in=relationship).select_related('source')
         else:
             return RelatedDocument.objects.none()