[leoc]

I seem to recall that Python not only didn't (doesn't?) have block scope, it tended (tends?) to produce a completely, blithely cryptic error message when the programmer assumes that it does have proper block scope and writes a program that fails as a result. Discovering that was memorable.

[a_bonobo]

Python 3 has changed the "standard" traceback to be more readable and include more information, maybe that one is more to your liking: http://blog.ionelmc.ro/2014/08/03/the-most-underrated-featur...