I have developed a workaround for the issue you reported. I am able to build your package without issue. I have submitted the updated package to testing and I would welcome any testing. In the meantime I will set up another complete el5 rebuild to double-check.
Alternately, I could simply remove the %clean magic entirely. RPM itself doesn't care if there's no %clean; it just leaves some cruft around when doing rpmbuild. Obviously mock won't care at all.
- J<