Tox 4 released today and is a complete rewrite with many backward
incompatible changes. We need to update a number of things to support
that in the zuul-jobs tox role and elsewhere. A possibly incomplete
list of what was changed in this commit to make this work:
* Don't run tox --showconfig with {{ tox_extra_args }} as -vv is
in tox_extra_args by default and results in interleaved debug
output in the ini output making it invalid ini content.
* Update the tox siblings tox config parser to look for renamed
environment dir locations.
* Stop using whitelist_externals and use allowlist_exteranls
because whitelist_externals is removed and external commands that
are not explicitly allowed produce errors.
* Make the tox version configurable in ensure-tox as some users
may not be able to easily upgrade to tox v4.
* Escape literal # chars in tox.ini as they are treated as comments
when in the command strings now.
https://github.com/tox-dev/tox/issues/2617
Change-Id: I38e13b4f13bb1b2d6fb7e5c70b708e9bb016a455
41153f0653