Python 3 - Skip a certain test for a particular (swig,python) combo.

Current versions of SWIG have a bug with Python 3 that causes
Python to assert when iterating over a generator.  This patch
skips the test for the right combination of Python version and
SWIG version.  I'm attempting to upstream a patch to SWIG to
fix this in a subsequent as-of-yet unreleased version, but
I don't know how long that will take.

llvm-svn: 253273