web.py on Google App Engine

I'm trying to get a web.py application running on GAE. I hoped that sth like the following might work

import web
from google.appengine.ext.webapp.util import run_wsgi_app

[...]

def main():
    app = web.application(urls, globals())
    run_wsgi_app(app)

But obviously the app object doesn't conform with the run_wsgi_app function's expectations. The error msg says sth like app has no __call__ function, so I tried passing app.run instead, but that didn't work either.

How can I make the call to run_wsgi_app work?