Fix py3k popen and locale test fails

A popen call is made in the Python 3 platform module which causes our
assertions for our mock'd popen to fail. Also fixing a locale issue to
use defaultlocale() rather than LC_ALL.

Co-Authored-By: Steve Kowalik <steven@wedontsleep.org>
Change-Id: I45cdf7d921fbca5f09e5f65bd69fcee83fb7c8e4