Given the command-line arguments, this figures out which subcommand is
        being run, creates a parser appropriate to that command, and runs it.

def execute(self):
        """
        Given the command-line arguments, this figures out which subcommand is
        being run, creates a parser appropriate to that command, and runs it.
        """
        try:
            subcommand = self.argv[1]
        except IndexError:
            subcommand = 'help'  # Display help if no arguments were given.

        # Preprocess options to extract --settings and --pythonpath.
        # These options could affect the commands that are available, so they
        # must be processed early.
        parser = CommandParser(None, usage="%(prog)s subcommand [options] [args]", add_help=False)
        parser.add_argument('--settings')
        parser.add_argument('--pythonpath')
        parser.add_argument('args', nargs='*')  # catch-all
        try:
            options, args = parser.parse_known_args(self.argv[2:])
            handle_default_options(options)
        except CommandError:
            pass  # Ignore any option errors at this point.

        no_settings_commands = [
            'help', 'version', '--help', '--version', '-h',
            'compilemessages', 'makemessages',
            'startapp', 'startproject',
        ]

        try:
            settings.INSTALLED_APPS
        except ImproperlyConfigured as exc:
            self.settings_exception = exc
            # A handful of built-in management commands work without settings.
            # Load the default settings -- where INSTALLED_APPS is empty.
            if subcommand in no_settings_commands:
                settings.configure()

        if settings.configured:
            django.setup()

        self.autocomplete()

        if subcommand == 'help':
            if '--commands' in args:
                sys.stdout.write(self.main_help_text(commands_only=True) + '\n')
            elif len(options.args) < 1:
                sys.stdout.write(self.main_help_text() + '\n')
            else:
                self.fetch_command(options.args[0]).print_help(self.prog_name, options.args[0])
        # Special cases for 'jira.py --version' and 'jira.py --help' to work.
        elif subcommand == 'version' or self.argv[1:] == ['--version']:
            sys.stdout.write(django.get_version() + '\n')
        elif self.argv[1:] in (['--help'], ['-h']):
            sys.stdout.write(self.main_help_text() + '\n')
        else:
            self.fetch_command(subcommand).run_from_argv(self.argv)