[3.2.x] Changed "Don't overuse count() or exists()" example to Python.
[3.2.x] Changed "Don't overuse count() or exists()" example to Python.

Backport of 8a642b88c31787fde612ba72d4b282e1c2444035 from master

koordinates/django,wkschwartz/django,wkschwartz/django,wkschwartz/django,wkschwartz/django,koordinates/django,koordinates/django,koordinates/django