Print the range of archived packets.

def print_packet_range():
    """Print the range of archived packets."""
    first_packet = next(iter(archive.list_packets()))
    last_packet = next(iter(archive.list_packets(descending=True)))
    print('First packet:', first_packet)
    print('Last packet:', last_packet)

    td = last_packet.generation_time - first_packet.generation_time
    print('Timespan:', td)