Hello,
I followed your instructions and have things set up. When I execute the script on the Pi itself, or enter the URL without the username and password I successfully get the message to try a user and pass arguments next time. My trouble comes in when I try and use the URL you give that should show me a list of variables. Of course I am using the IP address for my Pi and the correct credentials for my nest account. When I execute this I get a page that starts with '<class 'urllib2.HTTPError'>'. There is much more I can provide if it helps but it is quite long and didn't want to copy and paste it all if it wasn't necessary.
I would love to be able to get this working and would appreciate any help you may be able to provide!