Overridding to make updating the defaults after instantiation of
        the option parser possible, update_defaults() does the dirty work.

def get_default_values(self):
        """
        Overridding to make updating the defaults after instantiation of
        the option parser possible, update_defaults() does the dirty work.
        """
        if not self.process_default_values:
            # Old, pre-Optik 1.5 behaviour.
            return optparse.Values(self.defaults)

        defaults = self.update_defaults(self.defaults.copy())  # ours
        for option in self._get_all_options():
            default = defaults.get(option.dest)
            if isinstance(default, basestring):
                opt_str = option.get_opt_string()
                defaults[option.dest] = option.check_value(opt_str, default)
        return optparse.Values(defaults)