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

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

        self._wrapped = Settings(context_module, default_settings=global_context)