/**
  * Event handler for registration attempts; rejects the registration
  * if email field is missing.
  *
  * @param RegisterAction $action
  * @return bool hook result code
  */
 function onStartRegistrationTry($action)
 {
     $email = $action->trimmed('email');
     if (empty($email)) {
         $action->showForm(_m('You must provide an email address to register.'));
         return false;
     }
     // Default form will run address format validation and reject if bad.
     return true;
 }