private function findNonExistingUserGroupId()
    {
        $userGroupManager = $this->getUserGroupManager();
        for ( $i = 0; $i < 20; $i++ )
        {
            $id = uniqid('UserGroup#', true);
            if ( !$userGroupManager()->checkUserGroupExistence( $id ) )
            {
                return $id;
            }
        }

        throw new \Exception( 'Possible endless loop when attempting to find a new id for UserGroup.' );
    }