CI: Bump Python versions, fix tests.

[coveralls]

Pull Request Test Coverage Report for Build 5670116298

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.582%

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Totals
Change from base Build 1237970804:	0.0%
Covered Lines:	238
Relevant Lines:	239

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💛 - Coveralls

[Gadgetoid]

This, of course, totally ignores that I need to repackage everything to the latest standards demonstrated by https://github.com/pimoroni/boilerplate-python