I am having the same issue as you did. I am running Moodle v2.6 (Build: 20131118) on a shared hosting. (Blue Host).
I am still getting this error and unable to fix it. Can you please point out which line I should edit in the curlio.php file?
Here is the debug message:
Exception - Could not json decode the token
More information about this error
Error code: generalexceptionmessage
line 153 of /lib/google/auth/Google_OAuth2.php: Google_AuthException thrown
line 104 of /lib/google/auth/Google_OAuth2.php: call to Google_OAuth2->setAccessToken()
line 131 of /lib/google/Google_Client.php: call to Google_OAuth2->authenticate()
line 121 of /repository/googledocs/lib.php: call to Google_Client->authenticate()
line 62 of /repository/repository_callback.php: call to repository_googledocs->callback()
I am looking at the lib/Google/curlio.php file and am trying to figure out where to fix this issue.
Any help here would be greatly appreciated.