Gentoo's Bugzilla –
Attachment 645984 Details for
Bug 729388app-text/ronn-.0.7.3-r3 with dev-lang/ruby:2.5 - /usr/lib64/ruby/2.5.0/x86_64-linux/rbconfig.rb:13:in `<module:RbConfig>': ruby lib version (2.5.8) doesn't match executable version (2.4.10) (RuntimeError)