Comment 6 for bug 1886837

Reviewed: https://review.opendev.org/741383
Committed: https://git.openstack.org/cgit/openstack/python-tripleoclient/commit/?id=c20dcf9aeab45cd062c5cbe82c9c5baf9dc20684
Submitter: Zuul
Branch: stable/ussuri

commit c20dcf9aeab45cd062c5cbe82c9c5baf9dc20684
Author: Marios Andreou <email address hidden>
Date: Wed Jul 8 18:27:01 2020 +0300

    Fix package manager used during undercloud packages update

    As described in the related bug we need to use dnf instead of yum
    for centos8 otherwise it fails in the undercloud packages update.

    I am using the python version to determine - py3 is dnf. As part of
    discussion here when dnf isn't available fall back to yum.

    Found as part of the work in [1].

    Related-Bug: 1886837
    [1] https://tree.taiga.io/project/tripleo-ci-board/task/1817

    Change-Id: Idac62d37a19ee49f30936e20021a9dab5af40eec
    (cherry picked from commit 9c53cb3ef5ad513b05d4888552a3280e0eec43ca)