Fedora has both classworlds and plexus-classworlds. Upstream for both is codehaus, but the first has older codebase than the other. I have recently added Provides/Obsoletes: classworlds to plexus-classworlds package in rawhide and did some scratch builds. So far everything worked fine. I believe that classworlds should be retired in rawhide as most of its functionality is already provided by plexus-classworlds.
It turned that there is some incompatibility between classworlds and plexus-classworlds after all. Because of this I reverted my change to plexus-classworlds. This request is invalid, sorry for the fuss.