title: In GCM, what is the error id in onError (Context context, String errorId)
body: <p>In the GCM example for Android, the example GCMIntentService suggests Overriding the following method:</p>
  
  <blockquote>
    <p>onError(Context context, String errorId): Called when the device tries
    to register or unregister, but GCM returned an error. Typically, there
    is nothing to be done other than evaluating the error (returned by
    errorId) and trying to fix the problem.</p>
  </blockquote>
  
  <p>My question is, where does this error id come from? How do I determine if the error occurred on registration vs unregistering for example?</p>
  
  <p>The <a href="http://developer.android.com/reference/com/google/android/gcm/GCMBaseIntentService.html#onError%28android.content.Context,%20java.lang.String%29" rel="nofollow">GCMBaseIntentService</a> wasn't of much help either, specifying <code>errorId - error id returned by the GCM service.</code></p>