title: Why is urlfetch throwing Download Errors when calling some Google services?
body: <p>I've noticed that some Google services are blocking requests from App Engine servers, resulting in a urlfetch DownloadError. An example would be a feedproxy.google.com url (<a href="http://feedproxy.google.com/~r/blabbermouth/~3/cAk78LX4gJE/news.aspx" rel="nofollow noreferrer">http://feedproxy.google.com/~r/blabbermouth/~3/cAk78LX4gJE/news.aspx</a>, for example).</p>
  
  <p>This occurs on all the apps I've tried it on, including app IDs I've never used for any kind of url fetching before. This behavior also <strong>doesn't</strong> occur on the local SDK. This leads me to believe that this is a result of using any GAE IP address when making the request.</p>
  
  <p>The weird thing is that it results in the throwing of a DownloadError, instead of an error status_code in the successfully retrieved response. Using urlfetch or httplib locally works just fine, so this DownloadError I don't yet grok, or it's just a bug, in which case I'll file a ticket. </p>