```heinrich@berlin:~/mck/jruby$ ./mvnw clean
[INFO] Scanning for projects...
[ERROR] Internal error: org.jruby.exceptions.RaiseException: (NameError) uninitialized constant JRuby::Util -> [Help 1]
org.apache.maven.InternalErrorException: Internal error: org.jruby.exceptions.RaiseException: (NameError) uninitialized constant JRuby::Util
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:120)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.apache.maven.wrapper.BootstrapMainStarter.start (BootstrapMainStarter.java:39)
    at org.apache.maven.wrapper.WrapperExecutor.execute (WrapperExecutor.java:122)
    at org.apache.maven.wrapper.MavenWrapperMain.main (MavenWrapperMain.java:50)
Caused by: org.jruby.exceptions.RaiseException: (NameError) uninitialized constant JRuby::Util
    at org.jruby.RubyModule.const_missing (org/jruby/RubyModule.java:3370)
    at RUBY.<main> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/stringio.rb:2)
    at org.jruby.RubyKernel.require (org/jruby/RubyKernel.java:956)
    at RUBY.<main> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/rubygems/specification.rb:1)
    at org.jruby.RubyKernel.require (org/jruby/RubyKernel.java:956)
    at RUBY.<module:(root)> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/rubygems/specification.rb:17)
    at RUBY.<main> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/rubygems.rb:1)
    at org.jruby.RubyKernel.require (org/jruby/RubyKernel.java:956)
    at RUBY.<main> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/rubygems.rb:1389)
    at org.jruby.RubyKernel.load (org/jruby/RubyKernel.java:974)
    at RUBY.<main> (/Users/heinrich/mck/jruby/lib/ruby/stdlib/rubygems.rb:117)
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/InternalErrorException```