Handle 1.8 VS 1.9 differences in fetch exception.

src/about_hashes.rb

@@ -23,7 +23,7 @@ class AboutHashes < EdgeCase::Koan
   def test_accessing_hashes_with_fetch
     hash = { :one => "uno" }
     assert_equal "uno", hash.fetch(:one)
-    assert_raise(___(IndexError)) do
+    assert_raise(___(IndexError, KeyError)) do
       hash.fetch(:doesnt_exist)
     end