Stable train is in Extended maintenance state[1] and we need to cap stable/train with older Tempest. But because of oslo.utils version bump in Tempest 27.0.0 and 28.0.0 which is not compatible with stable/train upper constraints so these versions do not work in stable/train - https://zuul.opendev.org/t/openstack/build/1146c9ce9f474d0d82b99b48b61c531e Let's use the Tempest 26.1.0 which is also compatible with stable/train testing. Related-Bug: #1955418 Change-Id: I376be5f5a4d693aeaaf74ca5285269f796103c15