Fetch user data.

        Raise a ServerError if an error occurs in the request process.

        @param username the user's name.
        @param macaroons the encoded macaroons string.

def get_user(self, username, macaroons):
        """Fetch user data.

        Raise a ServerError if an error occurs in the request process.

        @param username the user's name.
        @param macaroons the encoded macaroons string.
        """
        url = '{}u/{}'.format(self.url, username)
        return make_request(url, timeout=self.timeout, macaroons=macaroons)