title: Error while using maven site plugin (AbstractMethodError)
body: <p>When trying to do a mvn site:run with this project:</p>
  
  <pre><code>&lt;project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"&gt;
  &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  &lt;groupId&gt;com.example&lt;/groupId&gt;
  &lt;artifactId&gt;test&lt;/artifactId&gt;
  &lt;version&gt;0.0.1-SNAPSHOT&lt;/version&gt;
  &lt;packaging&gt;war&lt;/packaging&gt;
  &lt;name&gt;test&lt;/name&gt;
  &lt;description&gt;test&lt;/description&gt;
  
  &lt;reporting&gt;
      &lt;plugins&gt;
          &lt;!-- Project Reports --&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-project-info-reports-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.7&lt;/version&gt;
          &lt;/plugin&gt;
  
          &lt;!-- Change report --&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
              &lt;artifactId&gt;changes-maven-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.0-beta-1&lt;/version&gt;
          &lt;/plugin&gt;
      &lt;/plugins&gt;
  &lt;/reporting&gt;
  </code></pre>
  
  <p></p>
  
  <p>I get the following error:</p>
  
  <pre><code>    [INFO] Scanning for projects...
  [INFO]                                                                         
  [INFO] ------------------------------------------------------------------------
  [INFO] Building test 0.0.1-SNAPSHOT
  [INFO] ------------------------------------------------------------------------
  [INFO] 
  [INFO] --- maven-site-plugin:3.0:run (default-cli) @ test ---
  2013-08-21 12:44:07.381:INFO::Logging to STDERR via org.mortbay.log.StdErrLog
  [INFO] configuring report plugin org.apache.maven.plugins:maven-project-info-reports-plugin:2.7
  [INFO] configuring report plugin org.codehaus.mojo:changes-maven-plugin:2.0-beta-1
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD FAILURE
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 2.477s
  [INFO] Finished at: Wed Aug 21 12:44:08 CEST 2013
  [INFO] Final Memory: 16M/179M
  [INFO] ------------------------------------------------------------------------
  [ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.0:run (default-cli) on project test: Execution default-cli of goal org.apache.maven.plugins:maven-site-plugin:3.0:run failed: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-site-plugin:3.0:run: java.lang.AbstractMethodError: null
  [ERROR] -----------------------------------------------------
  [ERROR] realm =    plugin&gt;org.apache.maven.plugins:maven-site-plugin:3.0
  [ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
  [ERROR] urls[0] = file:/home/user/.m2/repository/org/apache/maven/plugins/maven-site-plugin/3.0/maven-site-plugin-3.0.jar
  [ERROR] urls[1] = file:/home/user/.m2/repository/org/apache/maven/reporting/maven-reporting-exec/1.0.1/maven-reporting-exec-1.0.1.jar
  [ERROR] urls[2] = file:/home/user/.m2/repository/org/apache/maven/reporting/maven-reporting-api/3.0/maven-reporting-api-3.0.jar
  ...
  [ERROR] urls[39] = file:/home/user/.m2/repository/commons-lang/commons-lang/2.5/commons-lang-2.5.jar
  [ERROR] urls[40] = file:/home/user/.m2/repository/commons-io/commons-io/1.4/commons-io-1.4.jar
  [ERROR] Number of foreign imports: 1
  [ERROR] import: Entry[import  from realm ClassRealm[maven.api, parent: null]]
  [ERROR] 
  [ERROR] -----------------------------------------------------
  [ERROR] -&gt; [Help 1]
  [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/PluginContainerException
  2013-08-21 12:44:08.256:INFO::Shutdown hook executing
  2013-08-21 12:44:08.257:INFO::Shutdown hook complete
  </code></pre>
  
  <p>The error happens only after I add the changes-maven-plugin regardless of whether there is anything in src/changes/ or not. Up until now, I wasn't able to figure out what exactly the problem is. Can someone explain what I'm doing wrong here?</p>