Restore support for Python 3.8

[ale-rt]

I had to use this on a project today.
I am not interested on having this merged, because I want to not use Python 3.8 anymore.

Anyway, it might be useful to share the small patch needed to have it working on Python 3.8.

[mister-roboto]

@ale-rt thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[coveralls]

Pull Request Test Coverage Report for Build 14104191613

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.008%) to 97.705%

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Totals
Change from base Build 13881071572:	0.008%
Covered Lines:	235
Relevant Lines:	239

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💛 - Coveralls

[gforcada]

@ale-rt thanks for sharing it (though I have no need for it 😅 ) I converted the PR into a draft one, to ensure someone by accident does not merge it 👍🏾