code: def setup(self):
          
          try:
              subprocess.check_output(["hcitool", "clock"],
                                      stderr=subprocess.STDOUT)
          except subprocess.CalledProcessError:
              raise BackendError("'hcitool clock' returned error. Make sure "
                                 "your bluetooth device is powered up with "
                                 "'hciconfig hciX up'.")
          except OSError:
              raise BackendError("'hcitool' could not be found, make sure you "
                                 "have bluez-utils installed.")
docs: Check if the bluetooth controller is available.