[Linaro-validation] lava-tool CI job - how to get dependencies installed

Hello guys,

Can someone please review the job I created for running the lava-tool unit tests?

https://ci.linaro.org/jenkins/job/lava-tool/

The CI build script is very simple: virtualenv ci-build-venv ci-build-venv/bin/python ./setup.py test

My first try did not go well, since virtualenv is not installed:

https://ci.linaro.org/jenkins/job/lava-tool/1/console

What's the appropriate way to make sure virtualenv is installed? I presume I cannot add `apt-get install -q -y python-virtualenv` in the top of the build script ...