Write Python2 and Python3 compatible byte stream.

def write_bytes(out_data, encoding="ascii"):
    """Write Python2 and Python3 compatible byte stream."""
    if sys.version_info[0] >= 3:
        if isinstance(out_data, type("")):
            if encoding == "utf-8":
                return out_data.encode("utf-8")
            else:
                return out_data.encode("ascii", "ignore")
        elif isinstance(out_data, type(b"")):
            return out_data
    else:
        if isinstance(out_data, type("")):
            if encoding == "utf-8":
                return out_data.encode("utf-8")
            else:
                return out_data.encode("ascii", "ignore")
        elif isinstance(out_data, type(str(""))):
            return out_data
    msg = "Invalid value for out_data neither unicode nor byte string: {}".format(
        out_data
    )
    raise ValueError(msg)