[BUG] latest release breaks build(?)

[Andre601]

Describe the bug
The latest release (2.2.3) results in a failed build for me.

I'm using a GitHub Action setup to build and publish the page and it fails with the following errors: https://pastes.dev/XgfLt3mAAI

To Reproduce
Steps to reproduce the behavior:

1. Use 2.2.3
2. Execute mkdocs build

Expected behavior
Build should be successful

Screenshots

Environment (please complete the following information):

• OS: ubuntu
• Python version 3.7
• Plugin version 2.2.3

Additional context
The full workflow file used can be found here: https://github.com/Andre601/blog/blob/master/.github/workflows/deploy-preview.yml

Run fails at "Build Docs" which is just mkdocs build

[liang2kl]

Thank you for reporting the problem!

As discussed in https://stackoverflow.com/a/59217333, it happens in Python versions under 3.8. I will fix this later.

[liang2kl]

I've also updated the test workflow so that no future updates will break any supported versions, at least in the scope of the tests. :)