This patch set combines whitespace linter and pep8 together
(as both do code linting) into the same job by dropping the
.zuul.yaml whitespace-linter job and rolling it up into the
same pep8 tox.ini check, just like Deckhand [0].
[0] 0462b7b929/tox.ini (L106)
Change-Id: I31ed60adfd431157ffc96a0f4d5d77d54af37352