Add run of buildnml for POSTPROCESSING if postprocssing is turned on and available

[ekluzek]

I'm mainly thinking of CUPiD here, but this could be useful for any post-processing type workflow. "preview_namelists" could check if postprocssing files are available, and if so and RUN_POSTPROCESSING is true and if so run the buildnml for the post-processing suite.

A CUPiD issue that talks about this is here:

NCAR/CUPiD#371

[ekluzek]

Code would be something like this:

In preview_namelists.py in the create_naemlists subroutine:

# After the "for model in models:" Loop, before the "# Save namelists to docdir"
  # This is a bit from Case.flush:
  run_postprocess = case.get_value("RUN_POSTPROCESSING")
  if run_postprocess:
      _postprocessing_spec_file = case.get_value("POSTPROCESSING_SPEC_FILE")
          if _postprocessing_spec_file is not None:
              have_postprocessing = os.path.isfile(_postprocessing_spec_file)
          else:
             have_postprocessing = False

          # Run buildnml for the post-processing component if buildnml exists
          # NOTE: This copies the handling of buildnml for components in the section above
          if have_postprocessing:
            config_dir = os.path.dirname(_postprocessing_spec_file)
            cmd = os.path.join(config_dir, "buildnml")
            # NOTE: In order to name the specific postprocessing component, there would need to be
            # a new XML vaiable with something like POSTPROC_NAME
            compname = "postprocessor"
            logger.info("Create namelist for postprocessing component {}"..format(compname))
            import_and_run_sub_or_cmd(
                cmd,
                (caseroot),
                "buildnml",
                (self, caseroot, compname),
                config_dir,
                compname,
                case=self,
            )

The above would NOT save postprocssing files to CaseDocs unless they get copied to the $RUNDIR, and are in the list of files to copy. For CUPID, *.yml would need to be added to the list. And CUPID would need to copy the files to the RUNDIR as well as the cupid-postprocessing subdirectory under $CASEDIR.