I am aware of previous questions regarding mechanize + Google App Engine, What pure Python library should I use to scrape a website? and Mechanize and Google App Engine.
I managed to get mechanize code that runs on GAE, many thanks to MStodd, from GAEMechanize project http://code.google.com/p/gaemechanize/ and
If anybody needs the code, you can contact MStodd !
ps: the code is not on google code, so you have to contact the owner..
Cheers don