Python 3.7 environment fails to solve with `conda env update` in Github Actions test

[valeriupredoi]

test

This is a recurring issue. I'm looking into it right now.

Update - cause found

The problem is that the conda incubator task uses a patched env file:

name: esmvaltool
channels:
  - conda-forge
dependencies:
  - cartopy>=0.18
  - compilers
  - gdal
  - esmpy
  - 'esmvalcore>=2.3.0,<2.4'
  - 'iris>=3.0.2,<3.0.4'
  - 'matplotlib>3.3.1,<3.4'
  - mpich<3.4
  - cdo>=1.9.7
  - eccodes!=2.19.0
  - imagemagick
  - nco
  - ruamel.yaml
  - scikit-learn
  - ncl>=6.5.0
  - r-base>=3.5
  - r-docopt
  - r-lintr
  - r-styler
  - r-yaml
  - r-udunits2
  - python=3.7

instead of using the command conda create --name esmvaltool 'python=3.7' && conda env update --name esmvaltool which works fine - the env updateing from a Py39 env that requests a Py37 is rough and leads to insolvability - I am going to suggest to the devs change it, if they don't do it we'll have to change the test ourselves :beer:

[valeriupredoi]

snap! it took longer on me computer but it still did the trick, I'll try mamba instead of bugging the conda incubator guys for now