core-bundle/src/Resources/contao/dca/tl_user_group.php
public function addTemplateWarning()
	{
		if (Contao\Input::get('act') && Contao\Input::get('act') != 'select')
		{
			return;
		}

		$objResult = $this->Database->query("SELECT COUNT(*) AS cnt FROM tl_user_group WHERE modules LIKE '%\"tpl_editor\"%'");

		if ($objResult->cnt > 0)
		{
			Contao\Message::addInfo($GLOBALS['TL_LANG']['MSC']['groupTemplateEditor']);
		}
	}
public function addTemplateWarning()
	{
		if (Contao\Input::get('act') && Contao\Input::get('act') != 'select')
		{
			return;
		}

		$objResult = $this->Database->query("SELECT COUNT(*) AS cnt FROM tl_user_group WHERE modules LIKE '%\"tpl_editor\"%'");

		if ($objResult->cnt > 0)
		{
			Contao\Message::addInfo($GLOBALS['TL_LANG']['MSC']['groupTemplateEditor']);
		}
	}
Add a warning if there are users with access to the template editor.