Cannot import 'datatree.testing' with Xarray 2023.12.0

[flemmel]

Hello everybody,

It's not possible to import datatree.testing with the Xarray 2023.12.0

Here is the error message:

>>> import datatree.testing     # or from datatree.testing import assert_identical
ImportError: cannot import name 'ensure_warnings' from 'xarray.testing' 

[TomNicholas]

Thank you for raising this and alerting me! This is a manifestation of the fragility I warned about in #270. It is fixed by #294, and I'll issue a release with that fix shortly.