Fix a bug where images can't be pushed that would remove a dependency image.

endpoints/index.py

@@ -126,7 +126,9 @@ def create_repository(namespace, repository):
     if existing.docker_image_id in new_repo_images:
       added_images.pop(existing.docker_image_id)
     else:
-      existing.repositoryimage.delete()
+      logger.debug('Deleting existing image with id: %s' %
+                   existing.docker_image_id)
+      existing.delete_instance()
 
   for image_description in added_images.values():
     image = model.create_image(image_description['id'], repo)