The tox project has released a major version upgrade (v4) with some
backwards incompatible changes[0]. This has caused some problems for
the ensure-tox role (and the many tox-related jobs that use it) in
zuul-jobs.
Clark Boylan was able to address several of the compatibility issues
that affected how tox is used internally in the role[1] (e.g.,
siblings installation and log copying). But it became apparent that
some of the breaking changes are related to the configuration of
projects that use tox. For example, the "whitelist_externals" option
has been renamed and using the old option produces an error.
The ensure-tox role has, to date, not had a method for specifying what
version of tox to install, instead, always installing the latest. To
enable projects to upgrade their support to tox v4 at their own pace, we
are adding a new role variable, "ensure_tox_version" which can be used
to specify what tox version the ensure-tox role should install.
This variable has been added, and it currently defaults to "<4" so that
the latest tox 3.x version is installed.
On December 22, we will update the default to be "" (the empty string)
which will once again mean that ensure-tox will install the latest
version of tox[2].
We recommend that you use this time to update your tox configuration to
work with tox v4. If you are unable to do so before December 21, you
can set the "ensure_tox_version" variable to "<4" on your jobs.
[0] https://discuss.python.org/t/tool-tox-4-on-the-horizon/6537
[1] https://review.opendev.org/866935
[2] https://review.opendev.org/866943