With the release of Python 3.12.1 we stopped using stest in CI because 3.12.1 introduced a breaking API change to the unittest runner API that broke a dependency of stestr, testtools. This has been worked around with a new testtools release so we can restore using stestr in CI again which should improve test run throughput. This commit restores using stestr for the test CI jobs and local runs. The cibuildwheel config remains unchanged and uses the stdlib unittest runner still, just for simplicity so we don't need to install additional test dependencies.
With the release of Python 3.12.1 we stopped using stest in CI because 3.12.1 introduced a breaking API change to the unittest runner API that broke a dependency of stestr, testtools. This has been worked around with a new testtools release so we can restore using stestr in CI again which should improve test run throughput. This commit restores using stestr for the test CI jobs and local runs. The cibuildwheel config remains unchanged and uses the stdlib unittest runner still, just for simplicity so we don't need to install additional test dependencies.