title: com.google.android.gms.auth.GoogleAuthException: getToken(Unknown Source) exception
body: <p>In my Android application, I am trying to get google token to verify at my google app engine backend server. But I always get this exception :</p>
  
  <pre><code>com.google.android.gms.auth.GoogleAuthException: getToken(Unknown Source) exception
  </code></pre>
  
  <p>My code :</p>
  
  <pre><code>    private Account mAccount = AccountManager.get(this).getAccountsByType(GoogleAuthUtil.GOOGLE_ACCOUNT_TYPE)[0];
      private static final String SCOPE = "audience:server:client_id:" +Constants.WED_CLIENT_ID;
      String token = GoogleAuthUtil.getToken(LoginActivity.this, mAccount.name, SCOPE);
  </code></pre>
  
  <p>I have tried every solution proposed in Stackoverflow. </p>