def METHOD_NAME(self):
    """
    Check it correctly fails if the port given is not a PCU.
    """
    # Look for a device with a serial number not starting with 37
    paths = glob.glob("/dev/ttyACM*") + glob.glob("/dev/ttyUSB*")
    realpaths = set(os.path.join(os.path.dirname(p), os.readlink(p)) for p in glob.glob("/dev/ttyPMT*"))
    for p in paths:
        if p in realpaths:
            continue  # don't try a device which is probably a good one
        kwargsw = dict(KWARGS_PCU)
        kwargsw["port"] = p
        with self.assertRaises(IOError):
            dev = CLASS_PCU(**kwargsw)