/usr/lib/ruby/vendor_ruby/ is in ruby-libxml 2.7.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/libxml.rb
/usr/lib/ruby/vendor_ruby/libxml/
/usr/lib/ruby/vendor_ruby/libxml/error.rb
/usr/lib/ruby/vendor_ruby/libxml/xpath_object.rb
/usr/lib/ruby/vendor_ruby/libxml/reader.rb
/usr/lib/ruby/vendor_ruby/libxml/hpricot.rb
/usr/lib/ruby/vendor_ruby/libxml/sax_callbacks.rb
/usr/lib/ruby/vendor_ruby/libxml/schema.rb
/usr/lib/ruby/vendor_ruby/libxml/sax_parser.rb
/usr/lib/ruby/vendor_ruby/libxml/node.rb
/usr/lib/ruby/vendor_ruby/libxml/namespace.rb
/usr/lib/ruby/vendor_ruby/libxml/tree.rb
/usr/lib/ruby/vendor_ruby/libxml/html_parser.rb
/usr/lib/ruby/vendor_ruby/libxml/attr_decl.rb
/usr/lib/ruby/vendor_ruby/libxml/attr.rb
/usr/lib/ruby/vendor_ruby/libxml/parser.rb
/usr/lib/ruby/vendor_ruby/libxml/schema/
/usr/lib/ruby/vendor_ruby/libxml/schema/attribute.rb
/usr/lib/ruby/vendor_ruby/libxml/schema/type.rb
/usr/lib/ruby/vendor_ruby/libxml/schema/element.rb
/usr/lib/ruby/vendor_ruby/libxml/namespaces.rb
/usr/lib/ruby/vendor_ruby/libxml/ns.rb
/usr/lib/ruby/vendor_ruby/libxml/properties.rb
/usr/lib/ruby/vendor_ruby/libxml/attributes.rb
/usr/lib/ruby/vendor_ruby/libxml/document.rb
/usr/lib/ruby/vendor_ruby/1.9.1/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/libxml_ruby.so
/usr/lib/ruby/vendor_ruby/xml/
/usr/lib/ruby/vendor_ruby/xml/libxml.rb
/usr/lib/ruby/vendor_ruby/xml.rb