###  Summary

Describe the goal of this PR. Mention any related Issue numbers.

### Requirements (place an `x` in each `[ ]`)

* [ ] I've read and understood the [Contributing Guidelines](https://github.com/slackapi/python-slackclient/blob/master/.github/contributing.md) and have done my best effort to follow them.
* [ ] I've read and agree to the [Code of Conduct](https://slackhq.github.io/code-of-conduct).