/usr/lib/ruby/2.0.0/tktext.rb is in ruby2.0-tcltk 2.0.0.484-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4
# # tktext.rb - load tk/text.rb # require 'tk/text'