Comment 10 for bug 1751316

Reviewed: https://review.openstack.org/625572
Committed: https://git.openstack.org/cgit/openstack/openstack-ansible/commit/?id=e86956fec6c253307d0f974247477dd165a8f124
Submitter: Zuul
Branch: stable/pike

commit e86956fec6c253307d0f974247477dd165a8f124
Author: Jesse Pretorius <email address hidden>
Date: Fri Feb 23 17:34:41 2018 +0000

    Isolate the Ansible bootstrap

    As we move forward with the python build/install simplification,
    more of the config is being applied in the pip conf, rather than
    being given as CLI options in each ansible task. This is good
    for providing a consistent experience, but has side effects for
    things like the Ansible bootstrap.

    When bootstrapping Ansible, we want to make use of a specific
    set of constraints which is not polluted by additional config
    on the host. We do not want the constraints from the repo
    server because they happen to include a constraint for Ansible
    which clashes with our requirement. As such, we only want the
    native OpenStack upper-constraints.

    In this patch we use the --isolated CLI option to ignore the
    host's pip configuration. We also introduce the ability to set
    extra pip install options by using the PIP_OPTS environment
    variable. This can be used to set the installation to use an
    alternative pypi mirror, or for extra links, etc.

    Change-Id: Ic966bafd04c4c01b3d93851a0e3ec2c1f3312f28
    Closes-Bug: #1751316
    (cherry picked from commit 6b94b21e18181eab1eddb1f3040c430051871a20)