Apparently something is wrong with make install for beta 1 and the `zoneinfo` module is not installed with it (only _zoneinfo).

When I run a local build `./python -c "import zoneinfo"` works, but when I do `make install` I get ImportError:

  $ bin/python3 -c "import zoneinfo"
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
  ModuleNotFoundError: No module named 'zoneinfo'

I assume this wasn't caught earlier because Lib/test/test_zoneinfo is *also* not being installed.

The C extension, _zoneinfo, is installed properly. I don't know if it is working on Windows.

I think I found the problem: these directories are not included in the Makefile.pre.in LIBSUBDIRS variable: https://github.com/python/cpython/blob/a355a06fcc7ef2232736dceb012ae623335cd7ab/Makefile.pre.in#L1373

PR incoming.

FYI my notes about adding new files and directories in Python:
https://pythondev.readthedocs.io/files.html

Victor: Might be worth updating your notes to indicate that any subdirectory (not just test subdirectories) need to go into LIBSUBDIRS. zoneinfo uses a subdirectory for both the tests and the zoneinfo module, and *neither* were included in the installation in this case.

We have multiple "install" buildbot which only run tests on the *installed* Python. I understand that we missed the issue because not only the implementation was broken by "make install", but the whole test was missing as well :-p

> Victor: Might be worth updating your notes to indicate that any subdirectory (not just test subdirectories) need to go into LIBSUBDIRS.

Done.

New changeset 2abededbc4165d2daa14ae9d74b1f33cce0593d7 by Paul Ganssle in branch 'master':
bpo-40683: Add zoneinfo to LIBSUBDIRS (#20229)
https://github.com/python/cpython/commit/2abededbc4165d2daa14ae9d74b1f33cce0593d7

New changeset b5bd4358fc2dea2e7c84d0c56974627fc43217cd by Miss Islington (bot) in branch '3.9':
bpo-40683: Add zoneinfo to LIBSUBDIRS (GH-20229)
https://github.com/python/cpython/commit/b5bd4358fc2dea2e7c84d0c56974627fc43217cd

Victor has confirmed that this is working on Windows, so I think the current state of the 3.9 and master branches is now fixed.

The last question remaining is whether this justifies a quick b2 release (or if there's another mechanism for a "fixup" release like b1.post0). Łukasz, what do you think?

The beta releases are every three weeks now because of the release schedule being adjusted to allow Linux distributions to release the new version in the Autumn distributions.

I understand that you're eager to have your feature up and running. I feel like shipping the fixed version in beta2 will be sufficient. If we released a beta1.5 later in the week, that would be overkill given the already aggressive schedule as you'd then have a beta2 two weeks later, no?

No worries Łukasz, I figured it would be worth bringing up because normally the releases aren't so broken that they aren't usable in the common case. That said, this won't break any *existing* code, it'll just prevent people on Linux machines from using zoneinfo.

I don't think waiting 3 weeks is a big deal. I'm planning to release a backport soon anyway, and I expect people probably won't adopt new-in-3.9 modules without a backport during the beta period *anyway*, since they can't deploy any code using that feature to prod.

I'm going to resolve this issue. Thanks for the quick response Łukasz and for the quick review Victor!