fix argument handling

delorean_server.py

import sys
from datetime import datetime
from freezegun import freeze_time

from django.core.management import call_command
from django.core.management.commands.runserver import Command as RunServerCmd


class Command(RunServerCmd):
    """
    Handy wrapper to run the dev server while simulating an arbitrary date.
    Requires freezegun installed (https://github.com/spulec/freezegun).

    """
    def add_arguments(self, parser):
        # our own arg should be added before the call to super, so that it is
        # not confused with the following port number.
        parser.add_argument('date', type=str)
        super().add_arguments(parser)

    def handle(self, *args, **kwargs):

        try:
            date_string = kwargs['date']
            _ = datetime.strptime(date_string, '%Y-%m-%d')
        except ValueError:
            print('Invalid date format: %s' % date_string)
            sys.exit(1)

        with freeze_time(date_string):
            call_command('runserver', *args, **kwargs)