Reintroduce Python 3.8 support

[mbercx]

Fixes #268

[bosonie]

Hello @gmatteo, do you think it is possible to rapidly include this PR (and all the other ones that are opened) and make a release?
Only after that we will be able to make a release of aiida-common-workflows that will guarantee reproducibility of all the calculations of the paper we are publishing. The paper is ready and the editor is only waiting for our green light for publication.

[gmatteo]

Hello @gmatteo, do you think it is possible to rapidly include this PR (and all the other ones that are opened) and make a release? Only after that we will be able to make a release of aiida-common-workflows that will guarantee reproducibility of all the calculations of the paper we are publishing. The paper is ready and the editor is only waiting for our green light for publication.

Ok, I've just started working on the new release