Load the settings module pointed to by the environment variable. This
        is used the first time we need any settings at all, if the user has not
        previously configured the settings manually.

def _setup(self):
        """
        Load the settings module pointed to by the environment variable. This
        is used the first time we need any settings at all, if the user has not
        previously configured the settings manually.
        """
        settings_module = os.environ.get(ENVIRONMENT_SETTINGS_VARIABLE, 'settings')
        if not settings_module:
            raise ImproperlyConfigured(
                'Requested settings module points to an empty variable. '
                'You must either define the environment variable {0} '
                'or call settings.configure() before accessing the settings.'
                .format(ENVIRONMENT_SETTINGS_VARIABLE))

        self._wrapped = Settings(settings_module, default_settings=global_settings)