Failed to scout hudson.plugins.jabber.im.transport.JabberPublisher
java.lang.UnsupportedClassVersionError: org/jivesoftware/smack/Roster$SubscriptionMode : Unsupported major.minor version 51.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
	at jenkins.util.AntClassLoader.defineClassFromData(AntClassLoader.java:1138)
	at hudson.ClassicPluginStrategy$AntClassLoader2.defineClassFromData(ClassicPluginStrategy.java:756)
	at jenkins.util.AntClassLoader.getClassFromStream(AntClassLoader.java:1309)
	at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1365)
	at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1325)
	at jenkins.util.AntClassLoader.loadClass(AntClassLoader.java:1078)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
	at hudson.plugins.jabber.im.transport.JabberPublisherDescriptor.<clinit>(JabberPublisherDescriptor.java:75)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:270)
	at hudson.ExtensionFinder$Sezpoz.scout(ExtensionFinder.java:677)
	at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:337)
	at hudson.ExtensionList.load(ExtensionList.java:300)
	at hudson.ExtensionList.ensureLoaded(ExtensionList.java:253)
	at hudson.ExtensionList.iterator(ExtensionList.java:143)
	at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:336)
	at hudson.ExtensionList.load(ExtensionList.java:300)
	at hudson.ExtensionList.ensureLoaded(ExtensionList.java:253)
	at hudson.ExtensionList.get(ExtensionList.java:158)
	at hudson.PluginManager$PluginUpdateMonitor.getInstance(PluginManager.java:1203)
	at hudson.maven.PluginImpl.init(PluginImpl.java:58)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:622)
	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:105)
	at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:169)
	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
	at jenkins.model.Jenkins$7.runTask(Jenkins.java:885)
	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:701)