Drush make in Phing

drushmakephing.xml

<project name="mumblrmake" default="dl modules" description="Jenkins Mumblr Make">

    <target name="dl modules">
      <exec  command="drush make mumblr.make . --yes" error='error' checkreturn="true">
      </exec>
      <loadfile  property="en.error" file="error" />
      <if>
        <contains string="${en.error}" substring="warning" />
        <then>
          <property name="en.fail" value="Could not download all modules" />
        </then>
      </if>
      <fail if="en.fail" message="${en.fail}" />
    </target>

</project>