How to use the neo4j.v1.ServiceUnavailable function in neo4j

def use(self):
        """ Run a set of batch commands or start the tool in interactive mode.
        """
        if self.env.interactive:
            if version_info >= (3,):
                self.console.write_help(WELCOME)
            else:
                self.console.write_help(WELCOME, end=u"")

            try:
                self.env.connect(NEO4J_URI, NEO4J_USER, NEO4J_PASSWORD)
            except ServiceUnavailable:
                self.console.write_error("Service Unavailable: Unable to connect to database on %s" % NEO4J_URI)
                exit(1)

            self.interact()
        else:
            try:
                self.env.connect(NEO4J_URI, NEO4J_USER, NEO4J_PASSWORD)
            except ServiceUnavailable:
                self.console.write_error("Service Unavailable: Unable to connect to database on %s" % NEO4J_URI)
                exit(1)

            for arg in self.args[1:]:
                self.runsource(arg)

def __init__(self, uri, auth, secure=True, verbose=False):
        try:
            self.driver = GraphDatabase.driver(uri, auth=auth, encrypted=secure)
        except ServiceUnavailable as error:
            raise ConsoleError("Could not connect to {} ({})".format(uri, error))
        self.uri = uri
        self.history = FileHistory(HISTORY_FILE)
        self.prompt_args = {
            "history": self.history,
            "lexer": PygmentsLexer(CypherLexer),
            "style": style_from_pygments(VimStyle, {
                Token.Prompt: "#ansi{}".format(self.prompt_colour.replace("cyan", "teal")),
                Token.TxCounter: "#ansi{} bold".format(self.tx_colour.replace("cyan", "teal")),
            })
        }
        self.lexer = CypherLexer()
        self.result_writer = TabularResultWriter()
        if verbose:
            from .watcher import watch
            self.watcher = watch("neo4j.bolt")

def request(self, method, url, fields=None, headers=None, **urlopen_kw):
        from neo4j.v1 import ServiceUnavailable
        from urllib3.exceptions import MaxRetryError
        try:
            if self.verified:
                return self._http.request(method, url, fields, headers, **urlopen_kw)
            else:
                with catch_warnings():
                    simplefilter("ignore")
                    return self._http.request(method, url, fields, headers, **urlopen_kw)
        except MaxRetryError:
            raise ServiceUnavailable("Cannot send %s request to <%s>" % (method, url))

if not user:
            user = DEFAULT_USER
        while True:
            graph_service = GraphService(host=host, user=user, password=password, bolt=True)
            try:
                _ = graph_service.kernel_version
            except Unauthorized:
                password = getpass("Enter password for user %s: " % user)
            except Forbidden:
                if graph_service.password_change_required():
                    self.write("Password expired\n")
                    new_password = getpass("Enter new password for user %s: " % user)
                    password = graph_service.change_password(new_password)
                else:
                    raise
            except ServiceUnavailable:
                self.write("Cannot connect to %s\n" % graph_service.address.host)
                raise
            else:
                self.write("Connected to %s\n" % host)
                self.services[host] = graph_service
                break
        self.graph_service = self.services[host]
        self.run = self.graph_service.graph.run
        readline.set_completer(SimpleCompleter(self.graph_service, cypher_keywords).complete)
        return 0