I don't really understand which line of this caused the packaging problem, but please revert what you need to to fix xarray main! We can just keep releasing new minor versions until we get it right, don't worry about that.

Did the tests run? Close/ reopen.

This didn't cause the packaging issue, the packaging issue was caused by #6096 and the good old "Wait this isn't a python builtin, but I have it in each environment!"
Like pkg_resources which comes with setuptools, took me ages to find what was wrong back then (old setuptools version in that venv) 😅

Looks like the same error was there two days ago so it isn't dask 2022.01.1 since it only got released 16h ago

That was an upstream-dev build, so it could still be a dask issue.

I am closing this because it was not the issue of the test failure you saw in #6207.

That was an upstream-dev build, so it could still be a dask issue.

Ahhh I should have looked more closely.

Btw I installed an older dask version (conda install -c conda-forge dask-core=2022.1.0) and tests pass.
So I guess it is an issue with dask 2022.01.1.

At least it helps to narrow down the time when this appeared in dask. AFAICT the first occurrence was in the nightly upstream-dev build #6197.