Comment 3 for bug 1420934

I've been debugging the issue here, according to the steps (and the logs) which Renato provided me with.

So, a problem arises if the access token has expires and the refresh token (which can be used to request a new access token without UI interactions) is still valid, but the client application has been revoked access from https://myaccount.google.com/ (section "Connected apps and services"). In that case, here's the logs:

Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: oauth2plugin.cpp 111 OAuth2Plugin :
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: oauth2plugin.cpp 206 respondWithStoredToken : Stored token is expired
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: oauth2plugin.cpp 586 refreshOAuth2Token : "1/XXXX"
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: oauth2plugin.cpp 598 sendOAuth2PostRequest :
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: oauth2plugin.cpp 623 sendOAuth2PostRequest : Query string = QUrl( "?grant_type=refresh_token&refresh_token=1/XXXX&client_id=759250720802-4sii0me9963n9fdqdmi7cepn6ub8luoh.apps.googleusercontent.com&client_secret=juFngKUcuhB7IRQqHtSLavqJ" )
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: base-plugin.cpp 112 postRequest : Posting request: QUrl( "https://accounts.google.com/o/oauth2/token" )
Feb 13 15:02:15 ubuntu-phablet signonpluginprocess[13128]: ../../../../src/remotepluginprocess/remotepluginprocess.cpp 496 startTask operation is completed
Feb 13 15:02:16 ubuntu-phablet signonpluginprocess[13128]: base-plugin.cpp 152 handleNetworkError : error signal received: 302
Feb 13 15:02:16 ubuntu-phablet signonpluginprocess[13128]: base-plugin.cpp 167 handleNetworkError : Contents: "{#012 "error" : "invalid_grant",#012 "error_description" : "Token has been revoked."#012}"

So, this is a but in signon-plugin-oauth2, which should discard the refresh token and try the authentication again if some error happens while using the refresh token.