tripleo-ansible zuul checks require virtualenv on CentOS 8

[Luke Short]

Description
===========
In the "tripleo-ansible" repository, one of the Zuul playbooks is failing due to a missing "virtualenv" executable on CentOS 8 jobs.

Steps to reproduce
==================
* Run the "tripleo-ansible-centos-8-molecule-tripleo-modules" Zuul job.

Expected result
===============
It completes successfully.

Actual result
=============
The Zuul prepare playbook "zuul.d/playbooks/pre.yml" will fail.

Environment
===========
master

Logs & Configs
==============
Example error from https://f730065723c08f7ac086-88861b9d9400d056d1e59097cbe450ee.ssl.cf1.rackcdn.com/735962/10/check/tripleo-ansible-centos-8-molecule-tripleo-modules/bcf01b1/job-output.txt :
http://paste.openstack.org/show/794906/

[Luke Short (ekultails)]

There are a few related patches up to address this:
- https://review.opendev.org/#/c/735167/
- https://review.opendev.org/#/c/735267/

[Alex Schultz (alex-schultz)]

https://review.opendev.org/#/c/736332/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/train
Review: https://review.opendev.org/736381

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/736381
Committed: https://git.openstack.org/cgit/openstack/tripleo-ansible/commit/?id=4ca3bd9459da65553516c36ffa7e176bb9c6606b
Submitter: Zuul
Branch: stable/train

commit 4ca3bd9459da65553516c36ffa7e176bb9c6606b
Author: Alex Schultz <email address hidden>
Date: Wed Jun 17 12:31:41 2020 -0600

    Ensure pip is installed

    We need pip and virtualenv for molcule jobs. This was dropped recently
    in the base image so we need to handle this ourselves.

    Closes-Bug: #1883946
    Change-Id: Ie5ba86c4d8aa97959d7336886536dc1439ce54bd
    (cherry picked from commit 19ef86c627f6ae59b16b5a7c5cd99727ca705cf0)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/736380
Committed: https://git.openstack.org/cgit/openstack/tripleo-ansible/commit/?id=4d4ecfd194968f573045d8cc6d541ca56e0dda8e
Submitter: Zuul
Branch: stable/ussuri

commit 4d4ecfd194968f573045d8cc6d541ca56e0dda8e
Author: Alex Schultz <email address hidden>
Date: Wed Jun 17 12:31:41 2020 -0600

    Ensure pip is installed

    We need pip and virtualenv for molcule jobs. This was dropped recently
    in the base image so we need to handle this ourselves.

    Closes-Bug: #1883946
    Change-Id: Ie5ba86c4d8aa97959d7336886536dc1439ce54bd
    (cherry picked from commit 19ef86c627f6ae59b16b5a7c5cd99727ca705cf0)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/tripleo-ansible 0.6.0 release.