I've just started to use CodeNarc and Violations, and I can't make it work.
I get error in hudson job when it's trying to parse CodeNarc xml report:

ERROR: Publisher hudson.plugins.violations.ViolationsPublisher aborted due to exception
hudson.util.IOException2: Cannot parse target/test-reports/CodeNarcReport.xml
at hudson.plugins.violations.parse.AbstractTypeParser.parse(AbstractTypeParser.java:64)
at hudson.plugins.violations.ViolationsCollector.doType(ViolationsCollector.java:189)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:116)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:27)
at hudson.FilePath.act(FilePath.java:753)
at hudson.FilePath.act(FilePath.java:735)
at hudson.plugins.violations.ViolationsPublisher.perform(ViolationsPublisher.java:74)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:601)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:580)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:558)
at hudson.model.Build$RunnerImpl.post2(Build.java:157)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:528)
at hudson.model.Run.run(Run.java:1348)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:139)
Caused by: java.lang.NullPointerException
at hudson.plugins.violations.model.Violation.compareTo(Violation.java:192)
at hudson.plugins.violations.model.Violation.compareTo(Violation.java:8)
at java.util.TreeMap.put(TreeMap.java:545)
at java.util.TreeSet.add(TreeSet.java:238)
at hudson.plugins.violations.model.FullFileModel.addViolation(FullFileModel.java:24)
at hudson.plugins.violations.types.codenarc.CodenarcParser.parseFileElement(CodenarcParser.java:90)
at hudson.plugins.violations.types.codenarc.CodenarcParser.execute(CodenarcParser.java:47)
at hudson.plugins.violations.parse.AbstractTypeParser.parse(AbstractTypeParser.java:59)
... 16 more

It's the same with faux path set or not set.