tests: avoid sys.path hacks

[akx]

Don't manually hack sys.path in tests/__init__.py; instead do this. (pip install -e . before running tests will have the same end effect.)

[RunDevelopment]

LGTM! Thank you @akx!

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Man, I hate python. All of these stupid hacks and configurations just to work around the lack of proper relative imports. In JS/TS, I can just import the source file I need and that's that. Trivially simple.

[akx]

@RunDevelopment In JS/TS land, woe be you if you do import foo from '../node_modules/...' (as I've seen people do in the wild) and you end up with no types (and tsc lighting up), or the wrong module kind getting bundled, or multiple copies of the same module, etc., etc. It's not perfect on that side of the fence either.

Anyway, as mentioned, no hack would be necessary either if you run pip install -e ., so the package is installed in editable mode and is hooked up to your sys.path as a kind of a site-package. This was used to be called, back in the dark days, python setup.py develop.