Mention that `nonlocal` is for Python3.0 and up only
Mention that `nonlocal` is for Python3.0 and up only

tuturto/hy,adamfeuer/hy,timmartin/hy,ALSchwalm/hy,zackmdavis/hy,michel-slm/hy,mtmiller/hy,jakirkham/hy,algernon/hy,freezas/hy,kartikm/hy,paultag/hy,Tritlo/hy,gilch/hy