Make sure to decode manifests into utf-8 when necessary

This fixes a decoding error

test/registry/protocol_fixtures.py

@@ -1,3 +1,5 @@
+# -*- coding: utf-8 -*-
+
 import random
 import string
 
@@ -24,6 +26,20 @@ def basic_images():
   ]
 
 
+@pytest.fixture(scope="session")
+def unicode_images():
+  """ Returns basic images for push and pull testing that contain unicode in the image metadata. """
+  # Note: order is from base layer down to leaf.
+  parent_bytes = layer_bytes_for_contents('parent contents')
+  image_bytes = layer_bytes_for_contents('some contents')
+  return [
+    Image(id='parentid', bytes=parent_bytes, parent_id=None),
+    Image(id='someid', bytes=image_bytes, parent_id='parentid',
+          config={'comment': u'the Pawe\xc5\x82 Kami\xc5\x84ski image',
+                  'author': u'Sômé guy'}),
+  ]
+
+
 @pytest.fixture(scope="session")
 def different_images():
   """ Returns different basic images for push and pull testing. """