Partly fixes #725

[schlunma]

This PR fixes a part of #725.

@axel-lauer Can you test this please? I do no have an example right now. Thanks! 😄

[axel-lauer]

This change looks fine to me.

[bouweandela]

This doesn't look good to me. If you're going to use the derive function, that should be implemented for the variable that is requested. Issue #725 is not related to derive functionality, except that it uses the same custom CMOR tables. Therefore, a solution should be implemented separately from derive functionality.

[schlunma]

I know that this doesn't solve #725.

All this PR does is to restore the old state before #667, where it was possible to read custom CMOR tables from non-derived variables by setting derive: True in the recipe. It's not a new feature, just a fix to restore the old behavior...

[bouweandela]

And it makes a mess of the code by mixing functionality. Maybe you can try to implement the what I described here instead?

[schlunma]

Yes, I totally agree that this is no final solution. I just wanted to re-add the old workaround which was nice to use until a proper solution is implemented for this problem.