I am trying to implement OpenID as one preferred option to my next web app here
The code is taken from this tutorial and works if I use my openID from myopenid.com
Basically, you're not allowed to use a token produced for one site to authenticate to another. This is a security feature. (OK, the site which is allowed to see the OpenID identity could make an assertion accepted by the other site about your identity, but that's out-of-band w.r.t. OpenID.)
The URL you should use is just this:
https://www.google.com/accounts/o8/id