/usr/lib/ruby/ is in ruby-dep-selector 1.0.3-2build3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/dep_selector/
/usr/lib/ruby/vendor_ruby/dep_selector.rb
/usr/lib/ruby/vendor_ruby/dep_selector/densely_packed_set.rb
/usr/lib/ruby/vendor_ruby/dep_selector/dep_gecode.rb
/usr/lib/ruby/vendor_ruby/dep_selector/dep_selector_version.rb
/usr/lib/ruby/vendor_ruby/dep_selector/dependency.rb
/usr/lib/ruby/vendor_ruby/dep_selector/dependency_graph.rb
/usr/lib/ruby/vendor_ruby/dep_selector/error_reporter/
/usr/lib/ruby/vendor_ruby/dep_selector/error_reporter.rb
/usr/lib/ruby/vendor_ruby/dep_selector/error_reporter/simple_tree_traverser.rb
/usr/lib/ruby/vendor_ruby/dep_selector/exceptions.rb
/usr/lib/ruby/vendor_ruby/dep_selector/gecode_wrapper.rb
/usr/lib/ruby/vendor_ruby/dep_selector/package.rb
/usr/lib/ruby/vendor_ruby/dep_selector/package_version.rb
/usr/lib/ruby/vendor_ruby/dep_selector/selector.rb
/usr/lib/ruby/vendor_ruby/dep_selector/solution_constraint.rb
/usr/lib/ruby/vendor_ruby/dep_selector/version.rb
/usr/lib/ruby/vendor_ruby/dep_selector/version_constraint.rb