This package is mongst the ones listed in the "fails to build in mock" report
posted to fedora-extras-list and fedora-devel-list daily. The problem isn't
actually due to missing buildrequires, it's due to the ruby package in
development putting things in different places, which don't line up with the
%files list.

I have attached a patch that will fix this for rawhide whilst remaining
spec-compatible with FC5 ruby (and possibly older versions too).

The patch changes the hardcoded locations to use the ruby sitelib and sitearch
locations as described in the Packaging/Ruby page on the wiki.