Explicitly reply no update for factory clients w/o update.

autoupdate.py

 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from buildutil import BuildObject
 from xml.dom import minidom
 
 import os
 import shutil
 import sys
@@ skipping 244 matching lines @@
     if validate_checksums:
       if success is False:
         raise Exception('Checksum mismatch in conf file.')
       print 'Config file looks good.'
 
   def GetFactoryImage(self, board_id, channel):
     kind = channel.rsplit('-', 1)[0]
     for stanza in self.factory_config:
       if board_id not in stanza['qual_ids']:
         continue
+      if kind + '_image' not in stanza:
+        break
       return (stanza[kind + '_image'],
               stanza[kind + '_checksum'],
               stanza[kind + '_size'])
+    return (None, None, None)
 
   def HandleUpdatePing(self, data, label=None):
     web.debug('handle update ping')
     update_dom = minidom.parseString(data)
     root = update_dom.firstChild
     if root.hasAttribute('updaterversion') and \
         not root.getAttribute('updaterversion').startswith(
         'MementoSoftwareUpdate'):
       web.debug('Got update from unsupported updater:' + \
           root.getAttribute('updaterversion'))
@@ skipping 53 matching lines @@
       ok = self.BuildUpdateImage(latest_image_path)
       if ok != True:
         web.debug('Failed to build an update image')
         return self.GetNoUpdatePayload()
 
       hash = self.GetHash('%s/update.gz' % self.static_dir)
       size = self.GetSize('%s/update.gz' % self.static_dir)
 
       url = 'http://%s/static/update.gz' % hostname
       return self.GetUpdatePayload(hash, size, url)