irements
    resolve to the same name, we could otherwise end up with dependency
    links that point outside the Requirements set. parent_req must
    already be added. Note that None implies that this is a user
    supplied requirement, vs an inferred one.
:param extras_requested: an iterable of extras used to evaluate the
    environment markers.
:return: Additional requirements to scan. That is either [] if
    the requirement is not applicable, or [install_req] if the
    requirement is applicable and has just been added.
z6Ignoring %s: markers '%s' don't match your environmentNz+ is not a supported wheel on this platform.z+a user supplied req shouldn't have a parentz