non-google login credentials

[David Fritz]

So I am trying to merge data from adsense with data from the new youtube analytics api. The issue I am running into is that one of my clients says he logs into adsense without using his google credentials (i believe he uses a yahoo email address to log in), so when oauth2 authenticate him into the application, he gets an error when it tries to pull his adsense data. 

Is there a way to have adsense link this account? 

I assume if in order to get authentication for both adsense and youtube analytics, he would have to sign into authenticate for youtube, then sign out, and then run another oauth authentication for adsense?