logilab-common #86980 --coverage option of pytest [in-progress]

common/pytest.py reads:

try:
    from logilab.devtools.lib.coverage import Coverage
    parser.add_option('--coverage', dest="coverage", default=False,
                      action="store_true",
                      help="run tests with pycoverage (conflicts with --pdb)")
except ImportError:
    pass

Since devtools/lib/coverage.py was removed several versions ago, there is no chance to add this option.

Either fix it by using python-coverage or by removing it.