I've just started working with Google OAUTH2 in order to add a "Sign in with Google" button to my web site.
According to the "Google+ Platform Developer Policies" section B.2.a.III, if a user deletes their Google account, I must delete all personal information I obtained from the Google API relating to them.
Does this apply to my web application as well? And if so, how do I detect that a user's Google account no longer exists? Surely, a successful login will only occur if the Google account exists; so how can I tell if a previously existing account is no longer there?