Google Account Authentication APIs (ClientLogin, AuthSub and OAuth 1.0) are deprecated as per deprecation policy. http://googledevelopers.blogspot.com/2012/04/changes-to-deprecation-policies-and-api.html
Important: AuthSub has been officially deprecated as of April 20, 2012. It will continue to work as per our deprecation policy, but we encourage you to migrate to OAuth 2.0 as soon as possible.