Hide NotImplementedError for windows

440dc6b7e0 (commitcomment-24074203)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59749 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/io/nonblock/test_flush.rb

@@ -67,5 +67,6 @@ class TestIONonblock < Test::Unit::TestCase
       end
       assert_equal(false, w.nonblock?)
     }
+  rescue NotImplementedError
   end
 end if IO.method_defined?(:nonblock)