When I click the "Add to cart" button on a variable product, with no variation selected, the WooCommerce pops up an alert: "Please select some product options before adding this product to your cart.".
The problem is, it shows up as an Alert (browser window with Ok button). I would like to display it as a classic WooCommerce notice box within the page (or possibly to do some custom actions), but I am unable to find the responsible actions.
I tried to look for "single_add_to_cart_button". The theme is Shopkeeper, but I've looked for other themes and they seem to display it in the same manner - so I believe it is WooCommerce's default.
Any hints on how to achieve this?