The files/rpms/general:python-virtualenv explicitly
installed this package on Fedoras.
This package is not installed on other distros by devstack
by default.
If you stack/unstack the package gets reinstalled,
and confuses the system about the installed virtual-env version.
The uninstall works in CI, but it can be problematic when you do
reinstalls on the same machine.
The uninstall introduced by
834b804d3eda9029d3c66db0ab732a76a22ed08b, this commit deos not
has any reference to the external bug what it supposed to solve.
Related RDO thread started here:
https://www.redhat.com/archives/rdo-list/2015-March/msg00015.html
Change-Id: I4a723f179bdc28d39a4910fb9e3787e9e67c354b
802473e45a