Prestashop Code - How to Enable Debug

So you are working in your Prestashop store and suddenly you get a blank screen and now matter how many times you retry the screen is always blank… wtf? By this time you are already thinking that you are in a dead end and rushing to Google and/or Prestashop community for help. Why Prestashop Debug must be always Enabled during Development? When in production we want PHP to hide all the errors it finds.