Repositories that have ruby code have Gemfile. Example from mediawiki-selenium:
#ruby=ruby-2.1.1 #ruby-gemset=mediawiki_selenium source "https://rubygems.org" gemspec
The first two lines are for RVM. We do not officially recommend RVM any more. If a Gemfile starts with:
#ruby=ruby-(...) #ruby-gemset=(...)
the above two lines should be removed from the Gemfile.
The list of repositories where the change should be made:
https://github.com/search?q=org%3Awikimedia+%22ruby-gemset%22&type=Code