We have two diametrically opposed use cases amongst our user base.
The first are the folks who just need tox/virtualenv to pre-exist,
so that they can do things like run tests. Neither tox nor virtualenv
themselves are fundamental to the thing under test, but are tools
that need to exist.
The second are folks for whom tools like pip or virtualenv are
essential to the software (such as OSA). For these users, it is
important that the version of those match what they expect their
users get from the distro.
Up until now, we've been using the pip-and-virtualenv element from
DIB which installs distro versions of pip and virtualenv, then
overwrites them with pip installed versions of the same, doing what
it can to prevent subsequent distro installs of the packages from
breaking things. This produces a really strange environment for
our friends in teh second camp, but honestly is a weird scenarios
to wrap the head around.
Instead, remove ALL distro packages of pip and virtualenv. Then
install both via get-pip. But - also leave a cleanup script. Since
pip installs are pretty well self-contained, it's easy to remove
them with a simple "rm". This cleanup script can be run by folks
like OSA in their first pre-playbook in zuul, and then their jobs
can subsequently apt-get or dnf install python3-virtualenv or
whatever they want to do that is appropriate.
Change-Id: Ifd9062e5a87923093e84b3e4fc933dc08375df82
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