/usr/lib/ is in ruby-classifier-reborn 2.0.4-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/classifier-reborn/
/usr/lib/ruby/vendor_ruby/classifier-reborn/bayes.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/extensions/
/usr/lib/ruby/vendor_ruby/classifier-reborn/extensions/hasher.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/extensions/vector.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/extensions/vector_serialize.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/category_namer.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/version.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi/
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi/cached_content_node.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi/summarizer.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi/content_node.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn/lsi/word_list.rb
/usr/lib/ruby/vendor_ruby/classifier-reborn.rb