pep8: fix test for membership should be 'not in'

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
tests: py.test with doctests and coverage

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
git: ignore .cache directory

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>