Oops my bad, I forgot that I had downloaded the cobertura-1.9.4.1.jar locally so I had no issues after an ant clean but Buildbot had
So finally removes last change in framework/base/build.xml related to Cobertura

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1554018 13f79535-47bb-0310-9956-ffa450edef68