Comment 5 for bug 1731026

Reviewed: https://review.openstack.org/577382
Committed: https://git.openstack.org/cgit/openstack/kolla-ansible/commit/?id=ddd9d6ae6d1ab0d6fed100343b090d023878a19b
Submitter: Zuul
Branch: stable/queens

commit ddd9d6ae6d1ab0d6fed100343b090d023878a19b
Author: Mark Goddard <email address hidden>
Date: Thu Dec 7 11:44:05 2017 +0000

    Support virtualenv installation in baremetal role

    Installing python packages directly to the system site-packages can
    cause various problems, in particular when pip overwrites a system
    package. Python virtualenvs are one solution to this issue, as they
    allow python packages to be installed in an isolated environment.

    This change adds support to the baremetal role for installing python
    dependencies in a virtualenv. Typically we will need to enable use of
    system site-packages from within this virtualenv, to support the use of
    modules such as yum, apt, and selinux, which are not available on PyPI.

    The path to the virtualenv is configured via the 'virtualenv' variable,
    and access to site-packages is controlled via
    'virtualenv_site_packages'.

    When executing other kolla-ansible commands, the variable
    'ansible_python_interpreter' should be set to the python interpreter
    installed in 'virtualenv'. Note that this variable cannot be templated.

    Change-Id: I0741923065246f9c5b168059fcd66504f2753c41
    Related-Bug: #1731026
    (cherry picked from commit 69979efc2e75dc4ab8e8e41a7136afdb64df678d)