With the venv building in place we can actually
support ubuntu (for only building venvs and not for
building *.deb packages)
Run using something like:
$ ./smithy -a prepare -o conf/origins/kilo-venv-2015.1.0.yaml \
-p conf/personas/in-a-box/venv-all.yaml -v
Change-Id: I5d9d36ee17ca7be34d65dc8ac8e21236b9c3fa37
5193dc0cf5