String key = getMetadataKey(repository, file);

        return readLastUpdated(touchfile, key);
    }

    @Override
    public String getError(Artifact artifact, ArtifactRepository repository) {
        File touchFile = getTouchfile(artifact);
        return getError(touchFile, getRepositoryKey(repository));
    }

    @Override
    public void touch(Artifact artifact, ArtifactRepository repository, String error) {

     *
     * @return the error description
     */
    public String getError() {
        return error != null ? error : "Error code: " + returnCode;
    }

    /**
     * Sets the error message.
     *
     * @param error the error message
     */
    public void setError(String error) {
        this.error = error;
    }

    /**
     * Gets the return code.
     *

    }

    /**
     * Gets the error message.
     *
     * @return the error message
     */
    public String getError() {
        return error;
    }

    /**
     * Sets the error message.
     *
     * @param error the error message
     */
    public void setError(String error) {
        this.error = error;
    }

     *
     * @return the error description
     */
    public String getError() {
        return error != null ? error : "Error code: " + returnCode;
    }

    /**
     * Sets the error message.
     *
     * @param error the error message
     */
    public void setError(String error) {
        this.error = error;
    }

    /**
     * Gets the registration ID.
     *

        this.error = error;
        this.completed = true;
    }

    /**
     * Get error if request failed
     *
     * @return exception if failed, null if successful
     */
    public Exception getError() {
        return error;
    }

    /**
     * Check if request failed
     *
     * @return true if failed, false otherwise
     */
    public boolean hasFailed() {

                            edge.isResolved(),
                            edge.getTarget() == null
                                    ? null
                                    : edge.getTarget().getMd().getError());
                    MetadataGraphVertex newV = res.addVertex(newMd);
                    MetadataGraphVertex sourceV = res.addVertex(edge.getSource().getMd());

                    res.addEdge(sourceV, newV, edge);

                    
                    return registration;
                } else {
                    throw new IOException("Witness registration failed: " + response.getError());
                }
                
            } catch (Exception e) {
                log.error("Failed to register for witness notifications", e);
                throw new RuntimeException(e);
            }

                    return registration;
                } else {
                    String errorMsg = response != null ? response.getError() : "Response was null";
                    throw new IOException("Witness registration failed: " + errorMsg);
                }

            } catch (Exception e) {

        // Setup mock RPC response for failure
        WitnessRegisterResponse mockResponse = mock(WitnessRegisterResponse.class);
        when(mockResponse.isSuccess()).thenReturn(false);
        when(mockResponse.getError()).thenReturn("Registration failed");

        WitnessRpcClient mockRpc = mock(WitnessRpcClient.class);
        lenient().when(mockRpc.register(any(WitnessRegisterRequest.class))).thenReturn(mockResponse);

        assertViolations(result, 0, 4, 0);

        assertContains(result.getErrors().get(0), "duplicate execution with id a");
        assertContains(result.getErrors().get(1), "duplicate execution with id default");
        assertContains(result.getErrors().get(2), "duplicate execution with id c");
        assertContains(result.getErrors().get(3), "duplicate execution with id b");
    }

    @Test