Comment 6 for bug 1816022

RE on your latest comment:

>The backport was merged, so now tempest list-plugins is correctly executed.

>But the problem is that tempest-17.0 is installed instead of the master version, probably because >the constraints are enforced.

This seems a problem. we should not install tempest-17.0. It should be from the master. In all stable branch job testing, we install tempest from the master and apply the constraint from the master only.

This is the flow:
1. install tempest form master (until you explicitly change TEMPEST_BRANCH which is default to master in all stable branch). It applies the upper_constraint from the stable branch but that will be overridden in step2
2. configure tempest, here the created venv will install all dependency with master's upper_constraint. This change is not backported to pike. This is one backport needed.
3. install tempest plugins in same venv created above. Now tempest plugin use the stable branch upper_constraint [1]. This is problem.

We should install the tempest plugin also with master upper_constraint same as Tempest otherwise we will have version compatibility issue which is nothing but this bug.

[1] https://github.com/openstack-dev/devstack/blob/72f632222f6d90d3545b5d7ca48297da4218e2ea/lib/tempest#L676