title: dojo - programmatic way to show invalid message
body: <p>dojo newbie - giving it a shot.
  After submitting a form, If an error is returned from the server I would like to show that message on the dijit.form.ValidationTextBox</p>
  
  <pre><code>var user_email = dijit.byId("login_user_email");
  user_email.set("invalidMessage", data["result"]["user_email"]);
  //need to force show the tooltip but how???
  </code></pre>
  
  <p>Any help much appreciated.</p>