pep8: fix pep8 errors found with 'make pep8' on zesty.
This can also be seen by running pep8 in a tox environment, but as it is right now, our Makefile uses ./tools/run-pep8. That runs 'pep8', where our tox environment runs 'flake8'.
We should really resolve that difference, but for now I am just quickly committing the fix.