ruby/ruby — pull request #448 by JonRowe (2013-11-14 11:14:08+00:00)
Title: Undefine SimpleDelegator#open

Including `::Kernel.dup` brings across the #open method into
SimpleDelegator with undesirable consequences.

e.g.

```Ruby
class A
end
SimpleDelegator.new(A.new).open
# => NoMethodError: private method `open' called for #
```