rspec/rspec-core — pull request #1020 by JonRowe (2013-07-24 09:56:21+00:00)
Title: Improve gem loading to prevent mismatch

Ok this has bugged me long enough to improve it, this checks not only that a local dev directory exists, but that the version matches...

Which means it won't attempt to use 3.x against 2.99 etc which bundler won't let you do anyway.