[ruby/psych] require 'delegate' explicitly

https://github.com/ruby/psych/commit/51a9ce13db
2021-06-07 23:19:40 +02:00 · 2021-06-07 23:19:40 +02:00 · b11638eed2
--- a/test/psych/visitors/test_yaml_tree.rb
+++ b/test/psych/visitors/test_yaml_tree.rb
@ -1,5 +1,6 @@
 # frozen_string_literal: true
 require 'psych/helper'
+require 'delegate'

 module Psych
  module Visitors