systems without NIS

[Kirill Angelov]

Hello,

there are problems with python 2.7, 3.3 reinstall in systems without nis.
String

.if !exists(/usr/bin/ypcat) || defined(WITHOUT_NIS) # the world with NO_NIS

do nothing, because /usr/bin/ypcat is still exist after make delete-old, and 
option WITHOUT_NIS seems to be undefined (in my case it's specified at 
/etc/src.conf)

Imho, best solution is new option NIS for OPTIONS_DEFINE menu at python ports 
Makefile