dask and python-xarray removed from testing

Dear Diane, all,
both dask and python-xarray have been removed from testing on July the 
30th causing the removal of a relatively large stack of packages that 
rely on them.

Both dask and, most of all, python-xarray are an important part of the 
modern Python scientific stack, so, IMHO, it is a real pity to have them 
out of testing for so long time.

Apparently there is a quite complex (circular?) set of dependency 
involving at least dask, dask.distributed, python-sparse, python-xarray, 
python-pint, cfgrib.

The blocking issue seems to be 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1143631, a single unit 
test of the dask test suite that goes in timeout on a single 
architecture (armhf).

While te issue seems to be genuine it is a single, IMHO not fundamental, 
test on a single architecture, so, maybe, a temporary solution could be 
to just skip it to allow the migration.

I could quickly prepare a patch if the solution is considered acceptable.

Unfortunately, as a DM I do not have an immediate access to an armhf 
box. I could ask to get access to an armhf machine, but probably the 
process would take a little bit longer.

For a longer term solution, IMHO, the first step would be to update the 
(rather old) dask version che is currently in the Debian archive.
Some preliminary effort has been already started (see [1]), but probably 
more coordination is needed to complete the update.
The last time that I looked into it, one of the main problematic point 
was the unavailability of pyarrow for Python 3.14 and for some of the 
currently supported platforms. I'm pretty sure that the situation is 
evolved since then.

I would be more than willing to support the effort once we agree on the 
approach to follow.

Please just let me know how to proceed.


[1] https://lists.debian.org/debian-python/2026/04/msg00005.html

kind regards