Bundler.setup explodes in unlocked mode if the gem is not present

[wycats]

~/Code/Sites/bundler /master ☁ > bundle exec irb
/Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/resolver.rb:158:in `resolve': Could not find gem 'compass (= 0.10.0.rc1, runtime)' in any of the sources. (Bundler::GemNotFound)
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/resolver.rb:40:in `resolve'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/resolver.rb:39:in `catch'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/resolver.rb:39:in `resolve'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/environment.rb:55:in `resolve'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/environment.rb:59:in `resolve_locally'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/environment.rb:28:in `specs'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/environment.rb:69:in `specs_for'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/environment.rb:23:in `requested_specs'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/runtime.rb:18:in `setup'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler.rb:70:in `setup'
    from /Users/wycats/.rvm/gems/ruby-1.8.7-p249/gems/bundler-0.9.14/lib/bundler/setup.rb:8