Cat the failed tox-envs

Before failing the build we should print the problematic tox
environments into the console to make it easier for folks to
troubleshoot. We are still archiving the individual tox runs but the
console logs will now also contain the errors.

Issue: RELENG-611
Change-Id: Ie6fd132c0de69e8448d320d23daaed811a0d47a1
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>