According to the RFC:

If urllib2 gets a 302 in response to a request, it MUST send the *same*
request to the URI specified in the Location header, without modifying
the method, headers, or any data (urllib2 is not RFC compliant here)

In urllib2, a 301 and a 307 message should be handled just like a 302.

If urllib2 gets a 303 in response to a request, it MUST send a GET
request to the URI specified in the Location header (urllib2 is "half"
RFC compliant here, this only works if the original request WASN'T a
POST request)

I will code a complete patch to make urllib2 work as RFC Compliant as
possible. Whenever it's ready i'll send it.