recipe_arctic_ocean.yml fails to run

[bouweandela]

When I run the recipe recipe_arctic_ocean.yml, it fails with the following stack trace:

Traceback (most recent call last):
  File "/pf/b/b381141/src/esmvalgroup/esmvaltool/esmvaltool/diag_scripts/arctic_ocean/arctic_ocean.py", line 525, in <module>
    main(config)
  File "/pf/b/b381141/src/esmvalgroup/esmvaltool/esmvaltool/diag_scripts/arctic_ocean/arctic_ocean.py", line 493, in main
    run_hofm_plot(cfg, observations)
  File "/pf/b/b381141/src/esmvalgroup/esmvaltool/esmvaltool/diag_scripts/arctic_ocean/arctic_ocean.py", line 132, in run_hofm_plot
    plot_params = hofm_plot_params(cfg, hofm_var, var_number, observations)
  File "/pf/b/b381141/src/esmvalgroup/esmvaltool/esmvaltool/diag_scripts/arctic_ocean/arctic_ocean.py", line 97, in hofm_plot_params
    cmap = get_cmap(cfg['hofm_cmap'][var_number])
  File "/pf/b/b381141/src/esmvalgroup/esmvaltool/esmvaltool/diag_scripts/arctic_ocean/utils.py", line 235, in get_cmap
    raise ValueError('Get unrecognised name for the colormap `{}`.\
ValueError: Get unrecognised name for the colormap `Spectral_r`.                            Colormaps should be from standard matplotlib                             set or from cmocean package.

Here are some version numbers that might be relevant:

matplotlib-base           3.2.2
cmocean                   2.0

[koldunovn]

Matplolib change the handling of the colormap names. I will fix it.