/usr/lib/ is in ruby-htree 0.8+dfsg-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/htree/
/usr/lib/ruby/vendor_ruby/htree/container.rb
/usr/lib/ruby/vendor_ruby/htree/context.rb
/usr/lib/ruby/vendor_ruby/htree/display.rb
/usr/lib/ruby/vendor_ruby/htree/doc.rb
/usr/lib/ruby/vendor_ruby/htree/elem.rb
/usr/lib/ruby/vendor_ruby/htree/encoder.rb
/usr/lib/ruby/vendor_ruby/htree/equality.rb
/usr/lib/ruby/vendor_ruby/htree/extract_text.rb
/usr/lib/ruby/vendor_ruby/htree/fstr.rb
/usr/lib/ruby/vendor_ruby/htree/gencode.rb
/usr/lib/ruby/vendor_ruby/htree/htmlinfo.rb
/usr/lib/ruby/vendor_ruby/htree/inspect.rb
/usr/lib/ruby/vendor_ruby/htree/leaf.rb
/usr/lib/ruby/vendor_ruby/htree/loc.rb
/usr/lib/ruby/vendor_ruby/htree/modules.rb
/usr/lib/ruby/vendor_ruby/htree/name.rb
/usr/lib/ruby/vendor_ruby/htree/output.rb
/usr/lib/ruby/vendor_ruby/htree/parse.rb
/usr/lib/ruby/vendor_ruby/htree/raw_string.rb
/usr/lib/ruby/vendor_ruby/htree/regexp-util.rb
/usr/lib/ruby/vendor_ruby/htree/rexml.rb
/usr/lib/ruby/vendor_ruby/htree/scan.rb
/usr/lib/ruby/vendor_ruby/htree/tag.rb
/usr/lib/ruby/vendor_ruby/htree/template.rb
/usr/lib/ruby/vendor_ruby/htree/text.rb
/usr/lib/ruby/vendor_ruby/htree/traverse.rb
/usr/lib/ruby/vendor_ruby/htree.rb