Does this fix the failure?

Author: trinistr

core/io/buffer/map_spec.rb

@@ -261,6 +261,7 @@ def make_big_file_fixture
         @file = File.open(make_big_file_fixture, "r+")
         -> { IO::Buffer.map(@file, 17, IO::Buffer::PAGE_SIZE) }.should raise_error(ArgumentError, "Offset too large!")
       ensure
+        @file.close unless @file.closed?
         File.delete(@file.path)
       end
     end