python-slack-sdk: “Failed RTM connect” error when trying to connect to Slack with RTM API

Description

I have a slack app that I built using the RTM API, that was working fine last time I used it (in December). Now, without any code changes since then, when I try to run it RTM fails to connect.

I stumbled across the Migrating to 2.x wiki, and I’m seeing the same error with rtm_connect when I try to run the example 1.x code as I do when I run mine. I found people having similar issues, but unlike them, I am not on a Windows machine, and I am fairly certain I am using the correct token.

I’ve outlined the issue in detail in a SO question here

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I’ve read and understood the Contributing guidelines and have done my best effort to follow them.
• I’ve read and agree to the Code of Conduct.
• I’ve searched for any related issues and avoided creating a duplicate issue.

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Bug Report

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Reproducible in:

slackclient version: slackclient==1.3.2

python version: Python 3.8.0

OS version(s): Mac OS 10.14.6

Steps to reproduce:

Please see details, like steps taken and environment info and other context, outlined in StackOverflow question

Expected result:

What you expected to happen: RTM connects successfully

Actual result:

What actually happened: RTM connection fails

Attachments:

Logs, screenshots, screencast, sample project, funny gif, etc.