[PR] Switch to py38 as the primary CI version, keep py37 tested

[kopf-archiver]

A pull request by nolar at 2020-02-20 12:40:31+00:00
Original URL: zalando-incubator/kopf#314
Merged by nolar at 2020-02-20 14:09:35+00:00

What do these changes do?

Switch from Python 3.7 to 3.8 as the primary testing environment in Travis, and resolve few issues/warnings with 3.8. Python 3.7 compatibility is still tested and ensured.

Description

The testing is now organised this way:

• The latest Python — with all supported Kubernetes versions.
• The latest Kubernetes — with all supported Python versions (3.7 & 3.8 & optionally 3.9-dev).

We assume that if something breaks, it either breaks in the language (and one K8s version is enough to detect it), or in Kubernetes API (and one Python version is enough to detect it) — there is no need to test a real matrix "all Pythons vs. all K8ses".

Travis CI has a limit of 5 builds running in parallel (for us), so more than 5 or 10 builds delays the build results. Currently, we have 10 — and so it will be with the new grid (for a while).

Issues/PRs

Issues: #13

Type of changes

• Mostly CI/CD automation, contribution experience

Checklist

• The code addresses only the mentioned problem, and this problem only
• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt