rails/rails — pull request #14597 by matthewd (2014-04-04 13:29:23+00:00)
Title: Ensure we supply Kernel#y for 1.9 too

In 1.9, it doesn't live in its own file, so we'll have to define it ourselves.

Check RUBY_VERSION, instead of rescuing the require, because we want this to break if `psych/y` moves in a future Ruby release.