Error handler

    RuntimeError or ValueError exceptions raised by commands will be handled
    by this function.

def on_error(e):  # pragma: no cover
    """Error handler

    RuntimeError or ValueError exceptions raised by commands will be handled
    by this function.
    """
    exname = {'RuntimeError': 'Runtime error', 'Value Error': 'Value error'}
    sys.stderr.write('{}: {}\n'.format(exname[e.__class__.__name__], str(e)))
    sys.stderr.write('See file slam_error.log for additional details.\n')
    sys.exit(1)