Python 3 & Slack Client : ssl.SSLCertVerificationError

Question

I'm trying to access Slack in python 3.8 but i'm unable to pass the first step. Here is my code :

import slack

slack_token="xoxp-*******-*******-*******-*******"
client = slack.WebClient(slack_token)

client.chat_postMessage(
    channel="XXXXXXXXXX",
    text="Hello from your app! :tada:"
)

print('hello')

and here is the error:

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/aiohttp/connector.py", line 936, in _wrap_create_connection
    return await self._loop.create_connection(*args, **kwargs)  # type: ignore  # noqa
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/base_events.py", line 1046, in create_connection
    transport, protocol = await self._create_connection_transport(
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/base_events.py", line 1076, in _create_connection_transport
    await waiter
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/sslproto.py", line 529, in data_received
    ssldata, appdata = self._sslpipe.feed_ssldata(data)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/asyncio/sslproto.py", line 189, in feed_ssldata
    self._sslobj.do_handshake()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py", line 944, in do_handshake
    self._sslobj.do_handshake()
  ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1108)

venv config:

pip3 freeze
aiohttp==3.6.2
async-timeout==3.0.1
attrs==19.3.0
certifi==2019.11.28
chardet==3.0.4
idna==2.8
multidict==4.7.4
pipenv==2018.11.26
slack==0.0.2
slackclient==2.5.0
virtualenv==16.7.9
virtualenv-clone==0.5.3
yarl==1.4.2

Answer 1

Following instruction worked for me:

import ssl
import certifi
ssl_context = ssl.create_default_context(cafile=certifi.where())
client = slack.WebClient(token=os.environ['SLACK_TOKEN'], ssl=ssl_context)