At the command line:
curl -u ':USERNAME' -d '{"scopes":["public_repo"],"note":"Google Issues to GH"}' https://api.github.com/authorizations
curl -H "Authorization: bearer :TOKEN" https://api.github.com/users/:USERNAME -I
Replace :USERNAME
with your Github username and :TOKEN
with the oauth token you get from first curl
After that, the token will be listed in your Applications and you can revoke it from there