test_module.rb: workaround for ruby-mode.el

* test/ruby/test_module.rb (TestModule#test_undef): get rid of
  confusing ruby-mode.el by mixing special characters in //.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36734 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_module.rb

@@ -675,7 +675,7 @@ class TestModule < Test::Unit::TestCase
     end
 
     %w(object_id __send__ initialize).each do |n|
-      assert_in_out_err([], <<-INPUT, [], /warning: undefining `#{n}' may cause serious problems$/)
+      assert_in_out_err([], <<-INPUT, [], %r"warning: undefining `#{n}' may cause serious problems$")
         $VERBOSE = false
         Class.new.instance_eval { undef_method(:#{n}) }
       INPUT