Code errors on Xarray pages

[brian-rose]

The latest builds have code errors in several places in our Xarray tutorials, e.g.
https://foundations.projectpythia.org/core/xarray/computation-masking.html#groupby-split-apply-combine
and
https://foundations.projectpythia.org/core/xarray/computation-masking.html#compute-anomaly
and
https://foundations.projectpythia.org/core/xarray/enso-xarray.html#visualize-the-computed-nino-3-4-index

Several of these throw an error

TypeError: float() argument must be a string or a number, not 'cftime._cftime.DatetimeNoLeap'

I don't know when this started. These types of Python code errors don't get flagged by our CI tests. Is it due to version changes in Xarray or one of its dependencies?

[brian-rose]

I'm taking the liberty of labeling this as "high priority" because we should not have ugly errors in our featured tutorials!

[r-ford]

The nightly build for the CMIP6 Cookbook is also failing with the same error.

[ktyle]

I did some Xarray version testing. It looks like this behavior begins with the most recent (2022.11.0) xarray release. The immediate predecessor (2022.10.0) works without error.

I can put together a PR with an environment.yml that specifies xarray<2022.11.0 as a quick fix, although it would be worth digging deeper to see if this is a bug in Xarray or if the lines that are throwing the error need to be rewritten.

[ktyle]

suspect it stems from pydata/xarray#7052

[ktyle]

And it looks like the error goes away if we add
import nc_time_axis

[ktyle]

Looks like this problem will go away with the next release of Xarray, as it's been fixed with pydata/xarray#7276