title: Sonar Runner Execution Error
body: <p>I'm having a hard time figuring out how to fix this error I'm getting with the Sonar Runner on the Jenkins build server.  It's worked fine for me up until today.  I haven't changed any settings or files.  Does anyone know what I need to do to get this running again?</p>
  
  <blockquote>
    <p>ERROR: Error during Sonar runner execution
    org.sonar.runner.impl.RunnerException: Unable to execute Sonar
        at org.sonar.runner.impl.BatchLauncher$1.delegateExecution(BatchLauncher.java:79)
        at org.sonar.runner.impl.BatchLauncher$1.run(BatchLauncher.java:63)
        at java.security.AccessController.doPrivileged(Native Method)
        at org.sonar.runner.impl.BatchLauncher.doExecute(BatchLauncher.java:57)
        at org.sonar.runner.impl.BatchLauncher.execute(BatchLauncher.java:50)
        at org.sonar.runner.api.EmbeddedRunner.doExecute(EmbeddedRunner.java:71)
        at org.sonar.runner.api.Runner.execute(Runner.java:89)
        at org.sonar.runner.Main.executeTask(Main.java:70)
        at org.sonar.runner.Main.execute(Main.java:59)
        at org.sonar.runner.Main.main(Main.java:41)</p>
    
    <p>Caused by: java.lang.IllegalStateException: You must define the following mandatory properties for 'Unknown': sonar.projectKey, sonar.projectName, sonar.projectVersion
        at org.sonar.runner.batch.ProjectReactorBuilder.checkMandatoryProperties(ProjectReactorBuilder.java:314)
        at org.sonar.runner.batch.ProjectReactorBuilder.defineProject(ProjectReactorBuilder.java:130)
        at org.sonar.runner.batch.ProjectReactorBuilder.build(ProjectReactorBuilder.java:118)
        at org.sonar.runner.batch.IsolatedLauncher.createBatch(IsolatedLauncher.java:60)
        at org.sonar.runner.batch.IsolatedLauncher.execute(IsolatedLauncher.java:45)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.sonar.runner.impl.BatchLauncher$1.delegateExecution(BatchLauncher.java:75)
        ... 9 more</p>
  </blockquote>