Today I had a big problem: How to connect Google AppEngine application and Google BigQuery through oAuth2?
After I read all the documentation and make all the tests I didn’t found the way to connect AppEngine and BigQuery without the need of to do login on a Google Account or get the grant access screen.
I downloaded the oAuth2 python lib and I read the classes and methods, after test differents things I decided to talk with Joe Gregorio at Google.com: (http://firstname.lastname@example.org/) who explained me the best way to do that.
You can use AppAssertionCredentials for that:
Each App Engine application has an identity, and you should be able to add that identity to the ACLs for BigQuery.
Here is a sample on how to use AppAssertionCredentials on App Engine:
You can find the apps identity (email address) under the Service Account Name heading on the Application Settings page for the App Engine application.