from django.core.management.base import BaseCommand, CommandError

class Command(BaseCommand):

    help = "Useless command."

    def add_arguments(self, parser):

        parser.add_argument(

            "args",

            metavar="app_label",

            nargs="*",

            help="Specify the app label(s) to works on.",

        )

        parser.add_argument("--empty", action="store_true", help="Do nothing.")

    def handle(self, *app_labels, **options):

        app_labels = set(app_labels)

        if options["empty"]:

            self.stdout.write()

            self.stdout.write("Dave, I can't do that.")

            return

        if not app_labels:

            raise CommandError("I'm sorry Dave, I'm afraid I can't do that.")

        # raise an error if some --parameter is flowing from options to args

        for app_label in app_labels:

            if app_label.startswith("--"):

                raise CommandError("Sorry, Dave, I can't let you do that.")

        self.stdout.write("Dave, my mind is going. I can feel it. I can feel it.")