Dev Server: Require Memento Updater

Memento Updater: transmit new updaterversion tag so update server know
which update client this is.

Review URL: http://codereview.chromium.org/2024007
diff --git a/autoupdate.py b/autoupdate.py
index 161694f..aa543a9 100644
--- a/autoupdate.py
+++ b/autoupdate.py
@@ -250,6 +250,12 @@
     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'))
+      return self.GetNoUpdatePayload()
     query = root.getElementsByTagName('o:app')[0]
     client_version = query.getAttribute('version')
     channel = query.getAttribute('track')