CA-140596: Failed Lock cannot be garbage collected

Comments will rot, code is executed.

I did the same here: https://github.com/xapi-project/sm/blob/xs64bit/drivers/refcounter.py#L235

It's an application of http://refactoring.com/catalog/extractVariable.html

But if you think it should be obvious for everyone, that errno.ENOENT represents file not found, I can inline that.