def refresh(self, request):
        """Refresh the access token and scopes.

        Args:
            request (google.auth.transport.Request): The object used to make
                HTTP requests.

        Raises:
            google.auth.exceptions.RefreshError: If the Compute Engine metadata
                service can't be reached if if the instance has not
                credentials.
        """
        try:
            self._retrieve_info(request)
            self.token, self.expiry = _metadata.get_service_account_token(
                request,
                service_account=self._service_account_email)
        except exceptions.TransportError as caught_exc:
            new_exc = exceptions.RefreshError(caught_exc)
            six.raise_from(new_exc, caught_exc)
Refresh the access token and scopes.

        Args:
            request (google.auth.transport.Request): The object used to make
                HTTP requests.

        Raises:
            google.auth.exceptions.RefreshError: If the Compute Engine metadata
                service can't be reached if if the instance has not
                credentials.