Upgrade from 5.0.1 to 5.1 or 5.1.1 fails (in database upgrade)

[tux]

 Impossible to upgrade database

Migration failed: org/sonar/api/rules/ViolationFilter .
Please check logs.

=>

2015.06.06 10:30:34 INFO  web[DbMigration] ==  AddUuidToAnalysisReports: migrated (0.0870s) ==============================
2015.06.06 10:30:34 INFO  web[DbMigration]
2015.06.06 10:30:34 INFO  web[o.s.j.s.AbstractDatabaseConnector] Initializing Hibernate
2015.06.06 10:30:35 ERROR web[o.s.s.ui.JRubyFacade] Fail to upgrade database
org/sonar/api/rules/ViolationFilter
        java.lang.ClassLoader.defineClass1(Native Method)
        java.lang.ClassLoader.defineClass(ClassLoader.java:800)
        java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
        java.net.URLClassLoader.access$100(URLClassLoader.java:71)
        java.net.URLClassLoader$1.run(URLClassLoader.java:361)
        java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        java.security.AccessController.doPrivileged(Native Method)
        java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(ClassRealm.java:389)
        org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
        org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(ClassRealm.java:259)
        org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:235)
        org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:227)
        org.sonar.plugins.switchoffviolations.SwitchOffViolationsPlugin.getExtensions(SwitchOffViolationsPlugin.java:119)
        org.sonar.server.plugins.ServerExtensionInstaller.installExtensions(ServerExtensionInstaller.java:51)
        org.sonar.server.platform.ServerComponents.startLevel4Components(ServerComponents.java:819)
        org.sonar.server.platform.Platform.startLevel34Containers(Platform.java:120)
        org.sonar.server.platform.Platform.doStart(Platform.java:81)
        sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        java.lang.reflect.Method.invoke(Method.java:606)
        org.jruby.javasupport.JavaMethod.invokeDirectWithExceptionHandling(JavaMethod.java:440)
        org.jruby.javasupport.JavaMethod.invokeDirect(JavaMethod.java:304)
        org.jruby.java.invokers.InstanceMethodInvoker.call(InstanceMethodInvoker.java:52)
        org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:306)
        org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:136)
        org.jruby.ast.CallNoArgNode.interpret(CallNoArgNode.java:60)
        org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)
        org.jruby.ast.BlockNode.interpret(BlockNode.java:71)
        org.jruby.evaluator.ASTInterpreter.INTERPRET_METHOD(ASTInterpreter.java:74)
        org.jruby.internal.runtime.methods.InterpretedMethod.call(InterpretedMethod.java:139)
        org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:182)
        org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:306)
        org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:136)
        org.jruby.ast.CallNoArgNode.interpret(CallNoArgNode.java:60)
        org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)
        org.jruby.ast.BlockNode.interpret(BlockNode.java:71)
        org.jruby.ast.RescueNode.executeBody(RescueNode.java:221)
        org.jruby.ast.RescueNode.interpret(RescueNode.java:116)
        org.jruby.ast.BeginNode.interpret(BeginNode.java:83)
        org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)
        org.jruby.evaluator.ASTInterpreter.INTERPRET_BLOCK(ASTInterpreter.java:112)
        org.jruby.runtime.InterpretedBlock.evalBlockBody(InterpretedBlock.java:384)
        org.jruby.runtime.InterpretedBlock.yield(InterpretedBlock.java:336)
        org.jruby.runtime.BlockBody.call(BlockBody.java:73)
        org.jruby.runtime.Block.call(Block.java:101)
        org.jruby.RubyProc.call(RubyProc.java:290)
        org.jruby.RubyProc.call(RubyProc.java:228)
        org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:97)
        java.lang.Thread.run(Thread.java:745)