Tweak MavenProjectIntegrationTests

Log error output and force snapshot updates.

Author: philwebb

src/test/java/io/spring/asciidoctor/backend/integrationtest/MavenProjectIntegrationTests.java

@@ -45,6 +45,7 @@ void mavenBuild() throws Exception {
 		Invoker invoker = new DefaultInvoker();
 		invoker.setMavenHome(getMavenHome());
 		invoker.setOutputHandler(System.out::println);
+		invoker.setErrorHandler(System.err::println);
 		InvocationRequest request = createRequest();
 		InvocationResult result = invoker.execute(request);
 		File generatedDocs = new File(this.baseDirectory, "target/generated-docs");
@@ -68,6 +69,7 @@ private InvocationRequest createRequest() throws Exception {
 		request.setBaseDirectory(this.baseDirectory);
 		request.setUserSettingsFile(new File(this.baseDirectory, "settings.xml"));
 		request.setGoals(Arrays.asList("clean", "package"));
+		request.setUpdateSnapshots(true);
 		return request;
 	}