Failure to start plugin on TeamCity 9.1.4

[simonwilbert]

[2016-11-03 16:39:58,504] WARN - inLoader$TeamCityPluginContext - Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'mainAutowireCandidateResolver' defined in URL [jar:file:/C:/TeamCity/webapps/ROOT/WEB-INF/lib/common-impl.jar!/META-INF/teamcity-global-spring-candidate-resolver.xml]: Unsatisfied dependency expressed through constructor argument with index 0 of type [jetbrains.buildServer.spring.candidates.TeamCityAutowireCandidateResolver[]]: : Error loading class [com.enlivenhq.teamcity.SlackNotificator] for bean with name 'tcSlackNotificator' defined in plugin: teamcity-slack-integration#teamcity-slack-integration-1.0-SNAPSHOT.jar!/META-INF/build-server-plugin-teamcity-slack-integration.xml: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: com/enlivenhq/teamcity/SlackNotificator : Unsupported major.minor version 52.0; nested exception is org.springframework.beans.factory.CannotLoadBeanClassException: Error loading class [com.enlivenhq.teamcity.SlackNotificator] for bean with name 'tcSlackNotificator' defined in plugin: teamcity-slack-integration#teamcity-slack-integration-1.0-SNAPSHOT.jar!/META-INF/build-server-plugin-teamcity-slack-integration.xml: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: com/enlivenhq/teamcity/SlackNotificator : Unsupported major.minor version 52.0
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:747)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:185)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1115)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1018)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:229)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:175)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:611)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
at jetbrains.buildServer.plugins.spring.SpringPluginLoader.pluginClassesLoaded(SpringPluginLoader.java:95)
at sun.reflect.GeneratedMethodAccessor70.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at jetbrains.buildServer.util.EventDispatcher.dispatch(EventDispatcher.java:120)
at jetbrains.buildServer.util.EventDispatcher$2.invoke(EventDispatcher.java:67)
at com.sun.proxy.$Proxy16.pluginClassesLoaded(Unknown Source)
at jetbrains.buildServer.plugins.PluginManagerImpl$2.visitPlugin(PluginManagerImpl.java:137)
at jetbrains.buildServer.plugins.PluginsCollection.foreachLoadedPlugins(PluginsCollection.java:222)
at jetbrains.buildServer.plugins.PluginManagerImpl.firePluginClassesLoaded(PluginManagerImpl.java:135)
at jetbrains.buildServer.plugins.PluginManagerImpl.loadPlugins(PluginManagerImpl.java:81)
at jetbrains.buildServer.web.plugins.PluginManagerConfigurator.initializePlugins(PluginManagerConfigurator.java:14)
at jetbrains.buildServer.web.impl.BuildServerConfigurator.loadConfiguration(BuildServerConfigurator.java:40)
at jetbrains.buildServer.maintenance.TeamCityDispatcherServlet$WebApplicationCreatorAndDestroyer.createApplication(TeamCityDispatcherServlet.java:11)
at jetbrains.buildServer.maintenance.StartupProcessor.doApplicationStarting(StartupProcessor.java:374)
at jetbrains.buildServer.maintenance.StartupProcessor.processConcreteStage(StartupProcessor.java:690)
at jetbrains.buildServer.maintenance.StartupProcessor.processConcreteStageSafe(StartupProcessor.java:273)
at jetbrains.buildServer.maintenance.StartupProcessor.processTeamCityLifecycle(StartupProcessor.java:726)
at jetbrains.buildServer.maintenance.StartupProcessor.access$000(StartupProcessor.java:616)
at jetbrains.buildServer.maintenance.StartupProcessor$1.run(StartupProcessor.java:1)
at java.lang.Thread.run(Unknown Source)
Caused by: org.springframework.beans.factory.CannotLoadBeanClassException: Error loading class [com.enlivenhq.teamcity.SlackNotificator] for bean with name 'tcSlackNotificator' defined in plugin: teamcity-slack-integration#teamcity-slack-integration-1.0-SNAPSHOT.jar!/META-INF/build-server-plugin-teamcity-slack-integration.xml: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: com/enlivenhq/teamcity/SlackNotificator : Unsupported major.minor version 52.0
at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1328)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:594)
at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1394)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:385)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:354)
at org.springframework.beans.factory.BeanFactoryUtils.beanNamesForTypeIncludingAncestors(BeanFactoryUtils.java:187)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1006)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:889)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:862)
at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:811)
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:739)
... 33 more
Caused by: java.lang.UnsupportedClassVersionError: com/enlivenhq/teamcity/SlackNotificator : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at jetbrains.buildServer.plugins.classLoaders.TeamCityClassLoader.doLoadClass(TeamCityClassLoader.java:73)
at jetbrains.buildServer.plugins.classLoaders.TeamCityClassLoader.loadClass(TeamCityClassLoader.java:40)
at java.lang.ClassLoader.loadClass(Unknown Source)
at org.springframework.util.ClassUtils.forName(ClassUtils.java:246)
at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:395)
at org.springframework.beans.factory.support.AbstractBeanFactory.doResolveBeanClass(AbstractBeanFactory.java:1346)
at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1317)
... 43 more