Fix test

Author: yuki24

test/core_ext/name_error_extension_test.rb

@@ -39,14 +39,14 @@ def test_to_s_does_not_make_disruptive_changes_to_error_message
 
   def test_correctable_error_objects_are_dumpable
    error = begin
-             File.open('/tmp/file').sizee
+             File.open('./tmp/.keep').sizee
            rescue NoMethodError => e
              e
            end
 
    error.to_s
 
-   assert_equal "undefined method `sizee' for #<File:/tmp/file>", Marshal.load(Marshal.dump(error)).original_message
+   assert_equal "undefined method `sizee' for #<File:./tmp/.keep>", Marshal.load(Marshal.dump(error)).original_message
   end
 end