Now works with latest pytestcov
This transitively fixes beets which depends on soco, which now doesn't depend on
pytest_3 anymore, which depends on pytestcov_3, which is broken.
This is required for one of the plugins (sonosupdate) of Beets version
1.4.7.
I do not have a Sonos speaker, so I can't really test whether the
library works nor properly maintain this package (so I didn't add myself
as a maintainer).
I ran the build (including tests) against Python 2.x and Python 3.x.
Signed-off-by: aszlig <aszlig@nix.build>