Failed to send a request to Slack API server: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed

Question

I am trying to create a basic slack app following this tutorial. I have also created a slack app and generated the required tokens. But I am always getting below error. Please tell me where am I going wrong. My tokens seem correct.

Failed to send a request to Slack API server: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1124)>
Failed to send a request to Slack API server: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1124)>
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py", line 1350, in do_open
    h.request(req.get_method(), req.selector, req.data, headers,
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 1255, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 1301, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 1250, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 1010, in _send_output
    self.send(msg)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 950, in send
    self.connect()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py", line 1424, in connect
    self.sock = self._context.wrap_socket(self.sock,
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py", line 500, in wrap_socket
    return self.sslsocket_class._create(
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py", line 1040, in _create
    self.do_handshake()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py", line 1309, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1124)

My app.py

import os
from slack_bolt import App
from slack_bolt.adapter.socket_mode import SocketModeHandler

# Initializes your app with your bot token and socket mode handler
app = App(token=os.environ.get("SLACK_BOT_TOKEN"))

# Start your app
if __name__ == "__main__":
    SocketModeHandler(app, os.environ["SLACK_APP_TOKEN"]).start()

Answer 1

Adding following ssl_context helped me to solve issue:

import ssl
import certifi
ssl_context = ssl.create_default_context(cafile=certifi.where())

client = slack.WebClient(token=os.environ['SLACK_TOKEN'], ssl=ssl_context)

Answer 2

Anybody struggling with this on MacOS can look into: https://github.com/slackapi/bolt-python/issues/673