</goals>
            <configuration>
              <rules>
                <requireMavenVersion>
                  <version>3.0.5</version>
                </requireMavenVersion>
                <requireJavaVersion>
                  <version>1.8.0</version>
                </requireJavaVersion>
              </rules>
            </configuration>
          </execution>
        </executions>

                  <fileset dir="${project.build.directory}/guava-sources">
                    <contains text="@GwtCompatible"/>
                  </fileset>
                </copy>
                <!-- The following don't contain @GwtCompatible for dependency reasons. -->
                <copy toDir="${project.build.directory}/guava-gwt-sources">
                  <fileset dir="${project.build.directory}/guava-sources">