title: Failed build with message "Unable to instrument project."
body: <p>I build project by <code>mvn clean install cobertura:cobertura -X</code> and I it fails with this stacktrace:</p>
  
  <pre><code>[INFO] BUILD FAILURE
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 5:21.476s
  [INFO] Finished at: Tue Nov 26 09:21:28 CET 2013
  [INFO] Final Memory: 201M/7077M
  [INFO] ------------------------------------------------------------------------
  [ERROR] Failed to execute goal org.codehaus.mojo:cobertura-maven-plugin:2.6:instrument (default-cli) on project xcoll-integrated: Unable to instrument project. -&gt; [Help 1]
  org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:cobertura-maven-plugin:2.6:instrument (default-cli) on project xcoll-integrated: Unable to instrument project.
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:217)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
      at org.apache.maven.lifecycle.internal.MojoExecutor.executeForkedExecutions(MojoExecutor.java:365)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:199)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
      at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
      at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
      at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
      at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
      at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
      at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
      at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:597)
      at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
      at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
      at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
      at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
      at org.codehaus.classworlds.Launcher.main(Launcher.java:47)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:597)
      at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
  Caused by: org.apache.maven.plugin.MojoExecutionException: Unable to instrument project.
      at org.codehaus.mojo.cobertura.tasks.InstrumentTask.execute(InstrumentTask.java:151)
      at org.codehaus.mojo.cobertura.CoberturaInstrumentMojo.execute(CoberturaInstrumentMojo.java:162)
      at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
      ... 29 more
  [ERROR] 
  [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/MojoExecutionException
  [ERROR] 
  [ERROR] After correcting the problems, you can resume the build with the command
  </code></pre>
  
  <p>Any one have the same problem? I tried to find this in google but with no result. </p>
  
  <p>I am using <code>cobertura-maven-plugin 2.6</code>, <code>cobertura 2.0.3</code>, <code>java 1.6</code></p>