code: def _get_err_msg(row, col, fld, val, prt_flds):
          
          import traceback
          traceback.print_exc()
          err_msg = (
              "ROW({R}) COL({C}) FIELD({F}) VAL({V})\n".format(R=row, C=col, F=fld, V=val),
              "PRINT FIELDS({N}): {F}".format(N=len(prt_flds), F=" ".join(prt_flds)))
          return "\n".join(err_msg)
docs: Return an informative message with details of xlsx write attempt.