Add support for Python 3.8

[michael-k]

No description provided.

[ad-m]

@michael-k , I noticed that you have a long history of cooperation with this project. All your changes to the project are just done correctly. Will you allow me to give you direct write access to the repository? In this regard, I have obtained the approval of all other persons with such permissions.

I am writing here because this is your last contribution to the project and you have not published any contact details in your GitHub profile.

[michael-k]

Will you allow me to give you direct write access to the repository?

Yeah, sure. :)

I saw #603 and thought about the “commit bit” for some time, but my contributions were mostly pull requests. Since I value code reviews, the difference between having write access or not might not be significant.

[ad-m]

@michael-k Permissions granted. You now have the permissions, among others to accept others' changes, even if you don't want to be a judge in your own case.