Declare test dependencies in [test] extra

[cottsay]

Also introduce a constraints file to handle Python 2 in CI.

[nuclearsandwich]

Also introduce a constraints file to handle Python 2 in CI.

As I understand it, these constraints are for indirect dependencies which is why they aren't expressed directly in setup.py.
Does it make sense to place the file at the package root so that it's more readily discoverable for others building from source (especially in python2 environments)?

[cottsay]

Does it make sense to place the file at the package root...?

Eh, I could go either way. We could probably do that and then just drop it when we drop Python 2 support.

I'm 50/50 on this, so you'll have to be the deciding vote.

[nuclearsandwich]

We could probably do that and then just drop it when we drop Python 2 support.

Yeah that seems reasonable to me.

I'm 50/50 on this, so you'll have to be the deciding vote.

My overarching preference is for CI actions to "just run repository scripts" and thus the only contents stashed into CI subdirectories ought to be CI-only so let's move the constraints.txt file to the repo root.

[nuclearsandwich]

so you'll have to be the deciding vote.

by the by I very much appreciate making this explicit since my default tiebreaker is "implementing maintainers choice"

[cottsay]

...let's move the constraints.txt file to the repo root.

Done in 50636cf.

[nuclearsandwich]

Thanks for addressing review suggestions and answering questions!