Make conftest compatible with pytest 4.x
pytest 3.6 has deprecated get_marker in 3.6. The method was removed in 4.x
and replaced with get_closest_marker.
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Thomas Woerner <twoerner@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>