stack trace for java.lang.ClassNotFoundException: foo.RCPAppender

stack trace

	at 	java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at 	java.lang.Class.newInstance0(Class.java:355)
	at 	java.lang.Class.newInstance(Class.java:308)
	at 	org.eclipse.osgi.framework.internal.core.AbstractBundle.loadBundleActivator(AbstractBundle.java:151)
	at 	org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:751)
	at 	org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:370)
	at 	org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:284)
	at 	org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:417)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.setLazyTrigger(BundleLoader.java:265)
	at 	org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:106)
	at 	org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:453)
	at 	org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:216)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:393)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:469)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:422)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410)	
  at  org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
	at 	java.lang.ClassLoader.loadClass(ClassLoader.java:248)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.loadClass(BundleLoader.java:338)
	at 	org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:232)
	at 	org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:1197)
	at 	org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:174)
	at 	org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:904)
	at 	org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)
	at 	org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:55)
	at 	org.eclipse.core.internal.expressions.PropertyTesterDescriptor.instantiate(PropertyTesterDescriptor.java:92)
	at 	org.eclipse.core.internal.expressions.TypeExtension.findTypeExtender(TypeExtension.java:91)
	at 	org.eclipse.core.internal.expressions.TypeExtension.findTypeExtender(TypeExtension.java:124)
	at 	org.eclipse.core.internal.expressions.TypeExtension.findTypeExtender(TypeExtension.java:124)
	at 	org.eclipse.core.internal.expressions.TypeExtension.findTypeExtender(TypeExtension.java:124)
	at 	org.eclipse.core.internal.expressions.TypeExtensionManager.getProperty(TypeExtensionManager.java:114)
	at 	org.eclipse.core.internal.expressions.TestExpression.evaluate(TestExpression.java:96)
	at 	org.eclipse.ui.internal.services.EvaluationResultCache.evaluate(EvaluationResultCache.java:74)
	at 	org.eclipse.ui.internal.services.ExpressionAuthority.evaluate(ExpressionAuthority.java:165)
	at 	org.eclipse.ui.internal.services.EvaluationAuthority.addEvaluationListener(EvaluationAuthority.java:79)
	at 	org.eclipse.ui.internal.services.EvaluationService.addEvaluationListener(EvaluationService.java:47)
	at 	org.eclipse.ui.internal.activities.MutableActivityManager.updateActivity(MutableActivityManager.java:736)
	at 	org.eclipse.ui.internal.activities.MutableActivityManager.getActivity(MutableActivityManager.java:153)
	at 	org.eclipse.ui.internal.activities.ProxyActivityManager.getActivity(ProxyActivityManager.java:56)
	at 	org.eclipse.ui.internal.ActivityPersistanceHelper.loadEnabledStates(ActivityPersistanceHelper.java:236)
	at 	org.eclipse.ui.internal.ActivityPersistanceHelper.loadEnabledStates(ActivityPersistanceHelper.java:206)
	at 	org.eclipse.ui.internal.ActivityPersistanceHelper.<init>(ActivityPersistanceHelper.java:154)
	at 	org.eclipse.ui.internal.ActivityPersistanceHelper.getInstance(ActivityPersistanceHelper.java:122)
	at 	org.eclipse.ui.internal.Workbench.init(Workbench.java:1510)
 	at  org.eclipse.ui.internal.Workbench.access$34(Workbench.java:1472)
 	at  org.eclipse.ui.internal.Workbench$62.run(Workbench.java:2536)
Caused by: java.lang.ClassNotFoundException: foo.RCPAppender
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:506)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:422)
	at 	org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410)
	at 	org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
	at 	java.lang.ClassLoader.loadClass(ClassLoader.java:248)
	at 	ch.qos.logback.core.util.OptionHelper.instantiateByClassName(OptionHelper.java:46)
	at 	... 69 common frames omitted