@gen.coroutine
    def add_user(self, user):
        user_exists = yield gen.maybe_future(self.system_user_exists(user))
        if not user_exists:
            if self.create_system_users:
                yield gen.maybe_future(self.add_system_user(user))
            else:
                raise KeyError("User %s does not exist." % user.name)
        
        yield gen.maybe_future(super().add_user(user))
Create an HTTP server that calls `request_handler` on requests.
dataset/ETHPy150Open jupyterhub/jupyterhub/jupyterhub/auth.py/LocalAuthenticator.add_user--crossover with--dataset/ETHPy150Open dieseldev/diesel/diesel/protocols/http/core.py/HttpServer.__init__