안녕하세요. 좋은 책을 만나게 되어 기쁜 마음으로 공부하고 있습니다.
그런데 4-3에서 플라스크 웹서비스 개시에서 계속 로딩만 되고 실행이 되지 않습니다.

실행하면 아래와 같이 나오네요. 어떻게 하면 될지 알려주시면 감사하겠습니다.

• Serving Flask app "ratsnlp.nlpbook.classification.deploy" (lazy loading)
• Environment: production
  WARNING: This is a development server. Do not use it in a production deployment.
  Use a production WSGI server instead.
• Debug mode: off
  INFO:werkzeug: * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
  Exception in thread Thread-16:
  Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/urllib3/connection.py", line 159, in _new_conn
  (self._dns_host, self.port), self.timeout, **extra_kw)
  File "/usr/local/lib/python3.7/dist-packages/urllib3/util/connection.py", line 80, in create_connection
  raise err
  File "/usr/local/lib/python3.7/dist-packages/urllib3/util/connection.py", line 70, in create_connection
  sock.connect(sa)
  ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/local/lib/python3.7/dist-packages/urllib3/connectionpool.py", line 600, in urlopen
chunked=chunked)
File "/usr/local/lib/python3.7/dist-packages/urllib3/connectionpool.py", line 354, in _make_request
conn.request(method, url, **httplib_request_kw)
File "/usr/lib/python3.7/http/client.py", line 1281, in request
self._send_request(method, url, body, headers, encode_chunked)
File "/usr/lib/python3.7/http/client.py", line 1327, in _send_request
self.endheaders(body, encode_chunked=encode_chunked)
File "/usr/lib/python3.7/http/client.py", line 1276, in endheaders
self._send_output(message_body, encode_chunked=encode_chunked)
File "/usr/lib/python3.7/http/client.py", line 1036, in _send_output
self.send(msg)
File "/usr/lib/python3.7/http/client.py", line 976, in send
self.connect()
File "/usr/local/lib/python3.7/dist-packages/urllib3/connection.py", line 181, in connect
conn = self._new_conn()
File "/usr/local/lib/python3.7/dist-packages/urllib3/connection.py", line 168, in _new_conn
self, "Failed to establish a new connection: %s" % e)
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7f0cae896810>: Failed to establish a new connection: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/local/lib/python3.7/dist-packages/requests/adapters.py", line 449, in send
timeout=timeout
File "/usr/local/lib/python3.7/dist-packages/urllib3/connectionpool.py", line 638, in urlopen
_stacktrace=sys.exc_info()[2])
File "/usr/local/lib/python3.7/dist-packages/urllib3/util/retry.py", line 399, in increment
raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f0cae896810>: Failed to establish a new connection: [Errno 111] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/lib/python3.7/threading.py", line 926, in _bootstrap_inner
self.run()
File "/usr/lib/python3.7/threading.py", line 1177, in run
self.function(*self.args, **self.kwargs)
File "/usr/local/lib/python3.7/dist-packages/flask_ngrok.py", line 70, in start_ngrok
ngrok_address = _run_ngrok()
File "/usr/local/lib/python3.7/dist-packages/flask_ngrok.py", line 35, in _run_ngrok
tunnel_url = requests.get(localhost_url).text # Get the tunnel information
File "/usr/local/lib/python3.7/dist-packages/requests/api.py", line 76, in get
return request('get', url, params=params, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/requests/api.py", line 61, in request
return session.request(method=method, url=url, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/requests/sessions.py", line 530, in request
resp = self.send(prep, **send_kwargs)
File "/usr/local/lib/python3.7/dist-packages/requests/sessions.py", line 643, in send
r = adapter.send(request, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/requests/adapters.py", line 516, in send
raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f0cae896810>: Failed to establish a new connection: [Errno 111] Connection refused'))