Because bundler needs to support older versions of rubygems, we can't
actually rely on Gem::CIDetector (yet - in a year or so they might be
able to consolidate, if they don't change futher). So we're copying it
into the Bundler:: namespace, and enforcing that they stay completely in
sync with a test. No other tests are needed, since Gem::CIDetector is
already tested, and this is and will remain identical.

https://github.com/rubygems/rubygems/commit/abc67f0da1