black-ify code and add black to CI config
    
    Let's use the shiny new opinionated code formatter everyone's
    talking about:
    
    https://github.com/psf/black
    
    in addition to pylint, for now, because I think pylint may still
    catch stuff black doesn't. This reformats the code and tests to
    pass black, and adds a black check to the CI checks. We set the
    line length to 100 because that's the line length God intended,
    don't @ me. We turn off pylint's bad-continuation check because
    it and black disagree about how one style of continuation should
    work, there is a strong consensus that black's right and pylint
    is wrong, and pylint has actually given up and just removed this
    check entirely upstream now.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>