title: Sonarqube 4.0 unable to generate report
body: <p>I am trying to do sonar analysis on one of my projects but I am facing some issue when it comes to the very end of the mvn sonar:sonar command I am using Java 7 with maven 2.2.1 and sonar 4.0
  The error reported on screen is cannot execute sonar
  Unable to execute maven plugin.</p>
  
  <p>And further the trace says     Org.apache.maven.lifecycle.lifecycleExecutionException: cannot execute sonar</p>
  
  <pre><code> Caused by:org.apache.maven.plugin.mojoExecutionException: cannot execute sonar
  Caused by: org.sonar.api.utils.SonarException:unable to execute maven plugin.
  Caused by org.sonar.api.utils.SonarException:Unable to execute Maven 2 plugin
  Caused by Java.lang.reflect.InvoacationTargetException
  
  Caused by java.util.ConcurrentModificationException
  </code></pre>