Fixed deprecation warning for django 1.10

wagtailvideos/models.py

@@ -104,9 +104,9 @@ class AbstractVideo(CollectionMember, TagSearchable):
     def usage_url(self):
         return reverse('wagtailvideos:video_usage', args=(self.id,))
 
-    search_fields = TagSearchable.search_fields + CollectionMember.search_fields + (
+    search_fields = TagSearchable.search_fields + CollectionMember.search_fields + [
         index.FilterField('uploaded_by_user'),
-    )
+    ]
 
     def __str__(self):
         return self.title