Walk over key/value, tuples applying adjust_fn to files.

def _adjust_files(xs, adjust_fn):
    """Walk over key/value, tuples applying adjust_fn to files.
    """
    if isinstance(xs, dict):
        if "path" in xs:
            out = {}
            out["path"] = adjust_fn(xs["path"])
            for k, vs in xs.items():
                if k != "path":
                    out[k] = _adjust_files(vs, adjust_fn)
            return out
        else:
            out = {}
            for k, vs in xs.items():
                out[k] = _adjust_files(vs, adjust_fn)
            return out
    elif isinstance(xs, (list, tuple)):
        return [_adjust_files(x, adjust_fn) for x in xs]
    else:
        return xs