Comment 6 for bug 2002035

Reviewed: https://review.opendev.org/c/openstack/tripleo-heat-templates/+/868464
Committed: https://opendev.org/openstack/tripleo-heat-templates/commit/80dc72e26c2868fbeb6000897f5a16c6f7a6aa30
Submitter: "Zuul (22348)"
Branch: stable/wallaby

commit 80dc72e26c2868fbeb6000897f5a16c6f7a6aa30
Author: wu.shiming <email address hidden>
Date: Sat Sep 18 11:55:07 2021 +0800

    Changed minversion in tox to 3.18.0

    The patch bumps min version of tox to 3.18.0 in order to
    replace tox's whitelist_externals by allowlist_externals option:
    https://github.com/tox-dev/tox/blob/master/docs/changelog.rst#v3180-2020-07-23

    Also removes skipdist=True as in
    Ib0fca00c92ef56fce57eb6355cb6be36e478a744.

    Also inlcludes:

    Fix issues with tox 4.2.4

    tox now hard fails if there is mismatch in spec
    attributes[1]. This works around the issue
    temporarily. We probably have to drop py38 jobs
    and specify basepython for py39 target in the
    future.

    [1] https://github.com/tox-dev/tox/pull/2824/

    Conflicts:
            tox.ini

    Backport note:
    This is now required to adapt to the new tox 4.0 release, which no
    longer supports the old deprecated options.

    Closes-Bug: #2002035
    Change-Id: I5792c86745b875d074f670d92fe78a84a907bd74
    (cherry picked from commit 3cb006d53215d9b6e13f9671f8ad1c9c3648d1fd
     and 7fd4519b222166edc5a02121a4a04c113ab671be)
    (cherry picked from commit 0c0def6f81b6a71f2a07ae4bec9834d8048edb25)