Comment 8 for bug 1739440

Reviewed: https://review.openstack.org/582416
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=4acbf4fee389129611541b6d7db999dd5ddb45ad
Submitter: Zuul
Branch: master

commit 4acbf4fee389129611541b6d7db999dd5ddb45ad
Author: Julia Kreger <email address hidden>
Date: Thu Jul 12 15:43:15 2018 -0700

    ironic: provide facilities to gracefully navigate versions

    For quite some time, the nova virt driver has invoked the ironic
    python client library with a static microversion pin which causes
    operators to have a failed nova-compute process upon out of order
    upgrades, as well as causes ironic's grenade CI jobs to break every
    cycle when the pin is changed to a version released in the current
    cycle due to established community agreement as well as the grenade
    testing framework limitations.

    In order to gracefully navigate this, python-ironicclient has
    accepted a list of possible versions to negotiate since 2.2.0.

    This patch provies a mechanism to validate if we are able to
    send a request that was added at a specific version, allowing for
    minimal code changes and for logic to only be centered around newer
    features being added.

    Change-Id: I440689a246538fbc8200687e40480d837b87eb7b
    Closes-Bug: #1739440