[web2py] how to get logout() to launch an ajax call

[weheh]

I want something like this to work, but it doesn't, obviously.

def logout():
    auth.logout()
    response.js = 'alert("goodbye world");'
    from gluon import HTTP
    HTTP(202)
    return dict()

I've also tried auth.settings.logout_onlogout = [onlogoutfunction]
but that's not working for me either.

Can anyone shed light on this, please? Thanks.