[v2.7.1 bugfix release] Unpin cf-units and port changes from PR 1770 into v2.7.x

[valeriupredoi]

These are changes (mostly) done in #1770 that will be needed into the release branch for v2.7.1 bugfix release. The only major change is inside the sample data test_multimodel.py that contains a number of previous-to-1770 changes.

[codecov]

Codecov Report

Merging #1855 (c23bf9e) into v2.7.x (578fb61) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           v2.7.x    #1855      +/-   ##
==========================================
- Coverage   91.02%   91.00%   -0.02%     
==========================================
  Files         207      207              
  Lines       11216    11216              
==========================================
- Hits        10209    10207       -2     
- Misses       1007     1009       +2     

Impacted Files	Coverage Δ
esmvalcore/cmor/check.py	97.38% <ø> (-0.38%)	⬇️
esmvalcore/preprocessor/_multimodel.py	96.15% <ø> (ø)

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[bouweandela]

It's a bit surprising that the tests pass without the new netCDF files added in #1770. Do you understand why, since you didn't add them?

[valeriupredoi]

It's a bit surprising that the tests pass without the new netCDF files added in #1770. Do you understand why, since you didn't add them?

I have seen this in the other PR too (the one with all the features in one basket), and I don't know why that is - let me have a look

[valeriupredoi]

Blast! The sample_data test is identical to the tests/unit/preprocessor/_multimodel/test_multimodel.py test, I must have conked up badly, let me figure that out

[valeriupredoi]

also @bouweandela note that we are git ignoring all .nc files from .gitignore so those files are not under git scrutiny unless we git add -f ... changes

[valeriupredoi]

OK all back to normal and sane changes vs #1770 😥

[bouweandela]

also @bouweandela note that we are git ignoring all .nc files from .gitignore so those files are not under git scrutiny unless we git add -f ... changes

I know, we've had some issues with people accidentally committing huge netcdf files in the past

[valeriupredoi]

also @bouweandela note that we are git ignoring all .nc files from .gitignore so those files are not under git scrutiny unless we git add -f ... changes

I know, we've had some issues with people accidentally committing huge netcdf files in the past

I remember 🤣 It's good we have that block