Missing netcdf4 library

[rogersamso]

The netcdf4 library is required to serialize external objects to netcdf files with the serialize_external_objects method from the Macro class.

[enekomartinmartinez]

Hi @rogersamso

netcdf4 library is in the optional dependencies list. I would keep it there so as not to increment the dependencies as most people may not use features that need it (serialize_external_objects and dataset output). I will, in any case, include in the documentation that this function requires netcdf4 library installation.

[rogersamso]

maybe a try except around the ds.to_netcdf would also be helpful, as the error message that it sends is not clear at all.

[enekomartinmartinez]

Yes, that will be nice. Could you take care of it, please?

[enekomartinmartinez]

I added info about the requirement in the installation.rst and functions docstring in the PR that will be merged tomorrow. Please let me know if you want to include the error message.

[rogersamso]

I think it would be useful, but I don't have the time. So do what you think is best.