test_function.rb: fix messages
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64091 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_function.rb: fix messages
failed conditions, with errno description.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64091 b2dd03c8-39d4-4d8f-98ff-823fe69b080e