[docs] [issue25517] regex howto example in "Lookahead Assertions"

Serhiy Storchaka added the comment: Note that lookbehind assertions still are not documented in Regular Expression HOWTO. The example that demonstrates negative lookahead assertion is ".*[.](?!bat$)[^.]*$". But then we should explain why ".*" is changed to "[^.]*". ---------- nosy: +akuchling, georg.brandl, serhiy.storchaka stage: -> needs patch versions: -Python 3.2, Python 3.3 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue25517> _______________________________________