Implement testing for all operating systems as GitHub Actions

[sahansk2]

Fixes #297 , replaces #298 , commits taken from #301

[sahansk2]

@sahansk2 Can you update this so that flake8 only runs once? For now, it's fine that the windows test uses bash, but we should fix that at some point (can you add an issue?). Also can you put all of the testing commits on another branch? I'd like to merge into master with that first, then get to reviewing this PR. Once we merge that branch into master, then it will be appropriate to merge master into this branch and do a review

If we want to run flake8 only once, it's probably best that a separate workflow is created for that.

[sahansk2]

@benthayer This is ready for review.

[benthayer]

@sahansk2 It looks like there's something weird going on with Windows testing. Can you take a look? It's getting a OSError('[WinError 6] The handle is invalid'), but I'm not sure what that means. Git can be accessed from the (bash) command line, as seen by the new test I added, so there must be something else going on

[sahansk2]

GitPython released 3.1.8 on September 3rd, which apparently broke Windows compatibility.

By the way: it might be better to lock GitPython at 3.1.7 for reasons other than compatibility, for a while at least.

[benthayer]

Interesting, go ahead and lock it in. We can deal with the upgrade later

…

On Sun, Sep 6, 2020, 3:11 PM Sahan Kumarasinghe ***@***.***> wrote: GitPython released 3.1.8 <https://pypi.org/project/GitPython/#history> on September 3rd, which apparently broke Windows compatibility. By the way: it might be better to lock GitPython at 3.1.7 for reasons other than compatibility, for a while at least. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#304 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABORCY753HXR64Y7WXZI2HLSEPUGTANCNFSM4QKCQVIQ> .

[sahansk2]

Yep, it's been locked in. @benthayer