Return string for CLI invocation of kal, for channel scan.

def build_kal_scan_channel_string(kal_bin, channel, args):
    """Return string for CLI invocation of kal, for channel scan."""
    option_mapping = {"gain": "-g",
                      "device": "-d",
                      "error": "-e"}
    base_string = "%s -v -c %s" % (kal_bin, channel)
    base_string += options_string_builder(option_mapping, args)
    return(base_string)