Satisfy testing on macOS

[amotl]

About

This is somehow related to crate/crash#343, it makes the test suite work on macOS.

On top of using conditional buildout configuration sections for pulling down the appropriate CrateDB distribution tarballs for other operating systems than Linux, it skips some tests currently not working on macOS. Windows support has not been verified yet, I am working on this on behalf of #388.

Summary of the changes

• Remove doctests about CrateLayer.from_uri as it does not honor the platform when building the download URL. Instead, re-add it as a unit tests which at least runs the function by mocking _download_and_extract into a noop.
• Discriminate between testing against CrateDB nightly (run on ubuntu-latest) and multi-platform tests against a specific version of CrateDB (run on both ubuntu-latest and macos-latest).
• Improve stability by using REFRESH TABLE appropriately.
• Use most recent CrateDB 4.5.0.

[amotl]

It looks like GHA is currently not able to access cdn.crate.io [1]. Downloading the latest CrateDB release tarball croaks with [Errno 104] Connection reset by peer. Has anyone seen that before?

 Downloading https://cdn.crate.io/downloads/releases/nightly/crate-latest.tar.gz
While:
  Installing crate.
Error: Error downloading extends for URL https://cdn.crate.io/downloads/releases/nightly/crate-latest.tar.gz: [Errno 104] Connection reset by peer
Error: Process completed with exit code 1.

[1] https://github.com/crate/crate-python/pull/386/checks?check_run_id=1322270579

[amotl]

Downloading the latest CrateDB release tarball croaks with [Errno 104] Connection reset by peer.

Downloading the release tarballs started working again.

Now the Test python-3.6 sqla: 1.1.15 CrateDB: nightly on ubuntu-latest section croaks [1] with

Failed doctest test for https.txt

So, #384 will hopefully heal that?

[1] https://github.com/crate/crate-python/pull/386/checks?check_run_id=1322310763

[amotl]

After re-running the tests, they apparently succeeded.

[mfussenegger]

Could we also add windows and macos to the build matrix in the github actions config?

[amotl]

Could we also add windows and macos to the build matrix in the github actions config?

That would be nice, right?

[amotl]

Could we also add windows and macos to the build matrix in the github actions config?

I just added macos-latest. For Windows, I am working on #388.

Because I have not been able to adjust the test matrix appropriately to run CrateDB nightly on ubuntu-latest, but a specific version like e.g. CrateDB 4.5.0 on macos-latest, I split the GHA recipe into two parts: One is for checking pull requests on all operating systems and another one is for checking against CrateDB nightly on regular intervals as configured through the cronjob-like scheduling configuration. That latter exclusively happens on ubuntu-latest, as nightly builds are not available for other operating systems than Linux.