I'm trying to figure out Foursquare's OAuth so I can have a user sign into my app. So far I found this tutorial: http://pkarl.com/articles/connect-foursquare-api-oauth-python/
Unfortunately, it doesn't work. I got the same error message the commenters were getting. If anyone knows what the tutorial did wrong or knows another way of authenticating a foursquare account with OAuth, I would love to hear!