New port: devel/py-backports.shutil_which

This package packports Python 3's shutil.which.
Layout copied from kai@'s py-backports.os

Usage:

try:

from shutil import which

except ImportError:

from backports.shutil_which import which

WWW: https://github.com/minrk/backports.shutil_which

Used in an attempt to enable multimedia/streamlink on py27,
because sysutils/py-shutilwhich uses an incompatible layout.