fix 122

[juliettelavoie]

Pull Request Checklist:

• pre-commit hooks are installed/active in my local clone ($ pre-commit install)
• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes stack_drop_nan broken by new xarray #122
• (If applicable) Documentation has been added / updated (for bug fixes / features)
• If a merge request has been made in parallel to this PR in xscen-notebooks, it is merged and the submodules have been updated.
• HISTORY.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• Adjust stack_drop_nan to new version of xarray.

Does this PR introduce a breaking change?

No, this returns the same thing as with the previous version of xarray.

Other information:

With the new version of xarray, lat and lon were dropped out of out on l.125 of utils. I removed drop-=True to recover the previous behaviour of keeping them as coordinates only.

[aulemahal]

Oh! Are you saying the drop=True was never doing anything up to the new xarray?
Anyway, we needn't worry too much about backward compatibility for now.

[juliettelavoie]

Not exactly. With old xarray , drop=True dropped the coords loc (necessary to write to file) but not lat et lon.
With new xarray, drop=True drops loc, lat and lon, but drop=False drops only loc.