def parseCommandLineArguments():
  """
  Set up command line parsing.
  """
  parser = argparse.ArgumentParser(description="Calculate parallax error for given G and (V-I)")
  parser.add_argument("gmag", help="G-band magnitude of source", type=float)
  parser.add_argument("vmini", help="(V-I) colour of source", type=float)

  args=vars(parser.parse_args())
  return args