Still happens periodically, even with the fix applied.
I thought it was fixed, but after a few reloads it happened again.
WARNING: /usr/www/users/tedohs/piwik/vendor/twig/twig/lib/Twig/Extension/Core.php(1560): Warning - constant(): Couldn't find constant Piwik::LABEL_ID_GOAL_IS_ECOMMERCE_CART - Piwik 3.1.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
WARNING: /usr/www/users/tedohs/piwik/vendor/twig/twig/lib/Twig/Extension/Core.php(1560): Warning - constant(): Couldn't find constant Piwik::LABEL_ID_GOAL_IS_ECOMMERCE_ORDER - Piwik 3.1.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)