
virtualenv is a requirement for tox, so it is installed when tobiko roles install tox. Besides, virtualenv is also defined in the openstack requirements upper-constraints.txt file, specifying which one is the virtualenv valid upper version. Due to this, virtualenv is removed from the task that upgrades other packages as part of the tobiko-ensure-python3 role. Change-Id: I41b76d7041face19635c9fd35e773b9144d25c30