I have a Maven project and FindBugs fails to run through it:

[INFO] Locale is en
[java] The following classes needed for analysis were missing:
[java] org.jgroups.stack.IpAddress
[java] Warnings generated: 1201
[java] Missing classes: 2
log4j:ERROR A "org.jboss.logging.appender.FileAppender" object is not assignable to a "org.apache.log4j.Appender" variable.
log4j:ERROR The class "org.apache.log4j.Appender" was loaded by
log4j:ERROR [hudson.remoting.RemoteClassLoader@7cb25b9d] whereas object of type
log4j:ERROR "org.jboss.logging.appender.FileAppender" was loaded by [hudson.remoting.RemoteClassLoader@798a1663].
log4j:ERROR Could not instantiate appender named "FILE".
[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] org/apache/xerces/parsers/SAXParser
Classloading from system classloader disabled
[INFO] ------------------------------------------------------------------------
[INFO] Trace
java.lang.NoClassDefFoundError: org/apache/xerces/parsers/SAXParser
at hudson.plugins.findbugs.parser.FindBugsParser.readXml(FindBugsParser.java:242)
at hudson.plugins.findbugs.parser.FindBugsParser.parse(FindBugsParser.java:202)
at hudson.plugins.findbugs.parser.FindBugsParser.parse(FindBugsParser.java:139)
at hudson.plugins.findbugs.parser.FindBugsParser.parse(FindBugsParser.java:99)
at hudson.plugins.analysis.core.FilesParser.parseFile(FilesParser.java:197)
at hudson.plugins.analysis.core.FilesParser.parseFiles(FilesParser.java:176)
at hudson.plugins.analysis.core.FilesParser.invoke(FilesParser.java:126)
at hudson.plugins.analysis.core.FilesParser.invoke(FilesParser.java:29)
at hudson.FilePath.act(FilePath.java:753)
at hudson.FilePath.act(FilePath.java:735)
at hudson.plugins.findbugs.FindBugsReporter.perform(FindBugsReporter.java:122)
at hudson.plugins.analysis.core.HealthAwareMavenReporter.postExecute(HealthAwareMavenReporter.java:202)
at hudson.maven.MavenModuleSetBuild$Builder.postExecute(MavenModuleSetBuild.java:822)
at hudson.maven.MavenBuilder$Adapter.postExecute(MavenBuilder.java:300)
at hudson.maven.agent.PluginManagerInterceptor$1MojoIntercepterImpl.callPost(PluginManagerInterceptor.java:170)
at hudson.maven.agent.PluginManagerInterceptor.executeMojo(PluginManagerInterceptor.java:183)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:569)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:539)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
at org.apache.maven.lifecycle.LifecycleExecutorInterceptor.execute(LifecycleExecutorInterceptor.java:65)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at hudson.maven.agent.Main.launch(Main.java:165)
at hudson.maven.MavenBuilder.call(MavenBuilder.java:165)
at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:744)
at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:688)
at hudson.remoting.UserRequest.perform(UserRequest.java:114)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:270)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassNotFoundException: Classloading from system classloader disabled
at hudson.remoting.RemoteClassLoader$ClassLoaderProxy.fetch2(RemoteClassLoader.java:399)
at sun.reflect.GeneratedMethodAccessor289.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at hudson.remoting.RemoteInvocationHandler$RPCRequest.perform(RemoteInvocationHandler.java:274)
... 7 more

(Sorry for JENKINS-8200. I hoped that I will be able to edit/comment issue if I clone it.)