if (!visited.add(a.getGroupId() + ':' + a.getArtifactId() + ':' + a.getBaseVersion())) {
                RepositoryException exception =
                        new RepositoryException("Artifact relocations form a cycle: " + visited);
                invalidDescriptor(session, trace, a, exception);
                if ((getPolicy(session, a, request) & ArtifactDescriptorPolicy.IGNORE_INVALID) != 0) {
                    return null;