This commit is used to exclude new python packages from being
installed during tox tests and protect our CI from sporadical
failures caused by new packages.
NOTE. I have used mitaka constraints intentionally, since we
need newere packages than specified in liberty's
upper-constraints.
Change-Id: Ide77400b8d77631eaafa8cbea0679a23104d1aed
Closes-bug: #1705310