Zarr v3 + updated xarray cause ` TypeError: cannot pickle 'module' object`

[jbusecke]

I noticed that some tests fail with

E           TypeError: cannot pickle 'module' object

in the XarrayReader

This seems to only happen with caching is enabled (and only for the netcdf store)! To show this I have added an additional parametrization to the app test fixture which runs all tests both with and without cache.

I did confirm that this error is introduced with the upgrade of either xarray or zarr here. When I just add the changes to conftest.py to main, all tests pass, so this was not a silent failure.

Ill move on here for now, but I would love to fix this issue here. @hrodmn do you have any intuition why the caching would not play nice with a new xarray or zarr version?

Originally posted by @jbusecke in #96 (comment)

[maxrjones]

pydata/xarray#10779 will fix this. We can also add import h5netcdf.core to our own reader code to not need to wait for the upstream fix.