Re-organize directory structure

[ilevkivskyi]

See discussion in #2491

This PR needs a mypy commit that supports new directory structure (including --custom-typeshed-dir for standard library) landed in mypy master, which may take another day or two.

cc @JukkaL

[ilevkivskyi]

OK, here is the situation: all tests pass, but I temporarily disabled two tests:

• Test stubs with pytype
• Run stubtest on stubs

Somehow mypy_primer passes, but it will still needs to be updated to support this.

This is now ready for review, I am aiming to land this tomorrow morning.

[srittau]

Thanks! LGTM, with one question.

[srittau]

Should we print a warning or even fail the test if mod is not in supported_versions?

[ilevkivskyi]

Yes, I think we should, I was thinking about allowing some unrelated files in that directory (like some scripts etc). But we actually should keep directory structure clean. I will update this and will also add in a separate PR later a test that ensures stdlib and stubs have strict directory structure.

[rchen152]

I believe I have pytype_test working again; it requires first a change to pytype itself (google/pytype#821), then an update to the test (26862d4). (It'll take at least a day for the pytype change to be reviewed and merged, so it still makes sense to disable pytype_test first and re-enable it later.)

[ilevkivskyi]

@rchen152 Great, thanks! I will then merge this now with pytype test disabled, and you can re-enable it whenever ready.

[Akuli]

Each stub now shows up with "1 contributor" on github, but if I look at the blame (by pressing b), I can see all contributors.

[ilevkivskyi]

Each stub now shows up with "1 contributor" on github, but if I look at the blame (by pressing b), I can see all contributors.

This is a GitHub bug I think git blame works correctly in this case (since these are pure file renames).