Short version: I can confirm that bug under linux, but the patch breaks nis module on solaris.
Linux machine is: Linux malhar 2.2.16-3smp #1 SMP Mon Jun 19 17:37:04 EDT 2000 i686 unknown
with python version from recent CVS. I see the reported bug and the suggested patch does fix the problem.
Sparc box looks like this: SunOS cfa0 5.8 Generic_108528-06 sun4u sparc SUNW,Ultra-Enterprise
using python2.0 source tree. The nis module works out of the box, but applying the suggested patch breaks it: 'nis.error: No such key in map'.