Merge RubyGems 3.0.0 from upstream.
https://blog.rubygems.org/2018/12/19/3.0.0-released.html
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66451 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Merge RubyGems 3.0.0 from upstream.
https://blog.rubygems.org/2018/12/19/3.0.0-released.html
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66451 b2dd03c8-39d4-4d8f-98ff-823fe69b080e