Programmatically log on to a website using GAE(Google Appengine)

In GAE, urllib2.urlopen() series methods eventually call GAE's urlfetch() to do the job. At the time this post is written, there's no way to let Urlfetch understand cookie.

After some time, I found a solution here. It worked fine by far. Maybe some day I'll improve his class to some extent. My next app will heavily use this function.