authentication and urllib help wanted

[Bruce Southey]

Hi,
I am currently using urllib (Python 2.1 under Linux) in cgi script as:

opened_url=urllib.urlopen('http://username:password@some_site','params')

When the username/password is incorrect, urllib (actually
FancyURLopener) requests for username and password.  I would like to
avoid this request so to trap any incorrect username/password
combinations.

Thanks for any assistance,
Bruce Southey