private static function deleteOldActivations(Module_Register $module)
 {
     $cut = time() - $module->getActivationThreshold();
     self::log('Deleting user activations older than ' . GWF_Time::displayTimestamp($cut));
     $table = new GWF_UserActivation(false);
     $result = $table->deleteWhere("timestamp<{$cut}");
     if (0 < ($nDeleted = $table->affectedRows($result))) {
         self::log(sprintf('Deleted %d old user activations.', $nDeleted));
     }
 }