Zuul jobs fail running tox 4

[Vasudeo Nimbekar]

Brief Description
-----------------
Zuul jobs use tox 4 as of Dec 22, 2022 and Mistral tox.ini files are not compatible
This was the change that turned on tox4
https://review.opendev.org/c/zuul/zuul-jobs/+/866943

Changes uploaded to gerrit for mistral will fail unless those files are updated.

Release notes for tox 4 are here
https://tox.wiki/en/latest/changelog.html

Issues:
 4.0.6 Fail on pass_env/passenv entries containing whitespace
 4.0.0 Remove deprecated configuration option whitelist_externals which was replaced by allowlist_externals

Steps to Reproduce
------------------
Upload a code change to gerrit

Expected Behavior
------------------
It should pass Zuul

Actual Behavior
----------------
It will probably fail, complaining about inability to find a standard unix command (like bash)

Timestamp/Logs
--------------

example of a zuul failures where whitelist_externals is still being used:

linters: 202 E failed with bash is not allowed, use allowlist_externals to allow it [tox/session/cmd/run/single.py:54]

example of a passenv containing spaces
tox.tox_env.errors.Fail: pass_env values cannot contain whitespace, use comma to have multiple values in a single line, invalid values found 'http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/mistral/+/868869

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Vasudeo Nimbekar <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/mistral/+/868866
Reason: duplicate

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/mistral/+/868869
Committed: https://opendev.org/openstack/mistral/commit/b30ff6f95525dc1dbdba1642ced07e008f58df14
Submitter: "Zuul (22348)"
Branch: master

commit b30ff6f95525dc1dbdba1642ced07e008f58df14
Author: Vasudeo Nimbekar <email address hidden>
Date: Thu Dec 29 17:43:45 2022 +0530

    Update tox.ini to work with tox 4

    This change will allow this repo to pass zuul now
    that this has merged:
    https://review.opendev.org/c/zuul/zuul-jobs/+/866943

    Tox 4 deprecated whitelist_externals.
    Replace whitelist_externals with allowlist_externals
    Tox 4 Fail on pass_env/passenv entries containing whitespace.
    Updated passenv with comma separated values
    Closes-Bug: #2000727

    Change-Id: I48859d5a1c8242a6a7d049c96f8dcabbf4c7c044

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/mistral 16.0.0.0b1 development milestone.