Merge pull request #18634 from mvdbeek/import_relabel_from_file_error_message

        if how_type == "tabular":

            # We have a tabular file, where the first column is an existing element identifier,

            # and the second column is the new element identifier.

            new_labels_dict = {}

            source_new_label = (line.strip().split("\t") for line in new_labels)

            new_labels_dict = dict(source_new_label)

            for i, label_pair in enumerate(source_new_label):

                if not len(label_pair) == 2:

                    raise exceptions.MessageException(

                        f"Relabel mapping file line {i + 1} contains {len(label_pair)} columns, but 2 are required"

                    )

                new_labels_dict[label_pair[0]] = label_pair[1]

            for dce in hdca.collection.elements:

                dce_object = dce.element_object

                element_identifier = dce.element_identifier