With python unit tests, you are basically testing the server. And the correct response from server is the redirect exception and not the redirected page itself. I would recommend you testing this behaviour in two steps:
- test if the first page/url throws correctly initialized (code, url) HTTPRedirect exception
- test contents of the second page (on which is being redirected)
But of course, if you insist, you can resolve the redirect in Try/Except by yourself by inspecting the exception attributes and calling testing method on target url again.