[web2py] Auth form custom errors

[Rhys]

I'm creating a custom drop down login form for all pages where the user 
isn't logged in. Once they try and login through this form if it 
is unsuccessful it redirects to the /user/login page with the auth.login 
form. How do I get a error if the login has resulted in an invalid login. 
As there are two forms I've tried also tried to do a form out of html so 
there is no form key. Still no luck. Is it s simple variable I can use to 
determine if it is successful?