- Handle missing images properly

- Add support for deleting directories
- Add a slew of tests for deletion of directories and other kinds of deletion and layering

endpoints/verbs.py

@@ -69,8 +69,9 @@ def get_squashed_tag(namespace, repository, tag):
   permission = ReadRepositoryPermission(namespace, repository)
   if permission.can() or model.repository_is_public(namespace, repository):
     # Lookup the requested tag.
-    tag_image = model.get_tag_image(namespace, repository, tag)
-    if not tag_image:
+    try:
+      tag_image = model.get_tag_image(namespace, repository, tag)
+    except model.DataModelException:
       abort(404)
 
     # Lookup the tag's image and storage.