when tempst venv is build, it use the master upper_contraint[1]
but when we install tempest plugin, it use branch upper_contraint.
This leads to mismatch the dependency version between tempest and required
tempest plugins setup.
Current flow after this change is:
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.
3. install tempest plugins in same venv created above. Now tempest plugin
will also use the master upper_constraint.
With this tempest venv which has all enabled plugin will be contsraint with
master.
[1] 72f632222f/lib/tempest (L590)
Change-Id: I89314e8391e8f26c622fc090cbe27997b3cf049a
Closes-Bug: #1816022
(cherry picked from commit 0d83e09464)
4f97c8a656