docs: private TablePopulationRequirements getMVHandlerInfoMessage(MaterializedViewHandlerInfo mvh) {
          if ( ! mvh.getIssafewithnonemptysources()) {
              TablePopulationRequirements retval;
              String viewName = mvh.getDesttable().getTypeName();
              String errorMessage = createViewDisallowedMessage(viewName, null);
              retval = new TablePopulationRequirements(viewName);
              retval.setErrorMessage(errorMessage);
              for (TableRef tref : mvh.getSourcetables()) {
                  String tableName = tref.getTable().getTypeName();
                  retval.addTableName(tableName);
              }
              return retval;
          }
          return null;
      }