DownloadError: ApplicationError: 5 in urlfetching twitter RSS on AppEngine

I'm playing with twitter statuses rss feed on Google AppEngine (in python). I perform a urlfetch and I systematically get a

DownloadError: ApplicationError: 5

when I deploy the app whereas ev开发者_JS百科erything is fine when I test it locally on my dev server.

I guess it's a timeout issue due to AppEngine limitations. I already extended urlfetch deadline to 10sec.

How can I work around this issue ?