Highlight background according to scope

Hi, for beginners it is important even in py :)

I've seen it in Greenfoot.org
Then in py based CodeCombat.com, Codesters.com

http://www.mdpi.com/electronics/electronics-05-00033/article_deploy/html/images/electronics-05-00033-g005-1024.png
https://adamasbasecs3.files.wordpress.com/2015/06/aaa.jpg