Lots of iris warnings in output since iris v3.8.0

[schlunma]

Since iris v3.8.0, our output log is full of warnings like this:

2024-03-19 17:24:45,708 UTC [1445139] WARNING /work/bd0854/b309141/miniforge3/envs/esm/lib/python3.11/site-packages/iris/fileformats/netcdf/saver.py:2860: IrisDeprecation: Saving to netcdf with legacy-style attribute handling for backwards compatibility.
This mode is deprecated since Iris 3.8, and will eventually be removed.
Please consider enabling the new split-attributes handling mode, by setting 'iris.FUTURE.save_split_attrs = True'.
  warn_deprecated(message)

It would be nice to fix this in time for our v2.11.0.

[schlunma]

Another one where they slightly changed the message:

WARNING [3682372] /work/bd0854/b309141/miniforge3/envs/esm/lib/python3.11/site-packages/iris/fileformats/_nc_load_rules/helpers.py:912: _WarnComboIgnoringCfLoad: Ignoring invalid units 'day as %Y%m%d.%f' on netCDF variable 'time'.

[valeriupredoi]

iris=3.9.0 is out just recently, here's a test run with it https://github.com/ESMValGroup/ESMValCore/actions/runs/8793057494/job/24130318327 - iris warnings seem just a wee bit fewer, but not significantly trimmed