Fixup migration

aleksis/core/migrations/0035_preference_model_unique.py

@@ -16,7 +16,7 @@ class Migration(migrations.Migration):
         PersonPreferenceModel = apps.get_model("core", "PersonPreferenceModel")
         SitePreferenceModel = apps.get_model("core", "SitePreferenceModel")
 
-        from dynamic_preferences import BasePreferenceModel
+        from dynamic_preferences.models import BasePreferenceModel
 
         models = [GroupPreferenceModel, PersonPreferenceModel, SitePreferenceModel]
 
@@ -33,7 +33,7 @@ class Migration(migrations.Migration):
                     found = False
                     for obj in objs:
                         if BasePreferenceModel.get_value(obj) == BasePreferenceModel.preference(obj).default or found:
-                            obj.delete()                    
+                            obj.delete()
                         else:
                             found = True