This 404 is expected by Docker, so don't use the "normal" abort for it.

endpoints/registry.py

@@ -2,7 +2,7 @@ import logging
 import json
 
 from flask import (make_response, request, session, Response, redirect,
-                   Blueprint)
+                   Blueprint, abort as flask_abort)
 from functools import wraps
 from datetime import datetime
 from time import time
@@ -259,7 +259,7 @@ def get_image_json(namespace, repository, image_id, headers):
     data = store.get_content(store.image_json_path(namespace, repository,
                                                    image_id, uuid))
   except IOError:
-    abort(404, message='Image data not found')
+    flask_abort(404)
 
   try:
     size = store.get_size(store.image_layer_path(namespace, repository,