If you run into an OP_RE error when running buildr, this means you have gems 1.3.6 and buildr 1.3.5. Easiest way to fix this is to patch buildr. I have added a page to the wiki describing the process, and linked to it from the Building instructions page. Once buildr 1.4 comes out we can remove them.
The error in question looks like this:
/usr/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2503:in `const_missing': uninitialized constant Gem::Requirement::OP_RE (NameError) from /usr/lib/ruby/gems/1.8/gems/buildr-1.3.5/lib/buildr/packaging/version_requirement.rb:24 from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require' ....
Here's how to fix it: https://fedorahosted.org/candlepin/wiki/PatchingBuildr
jesus
candlepin@lists.fedorahosted.org