The parser tells you that the XML is not very well formed, but this error usually indicates that nothing was created before running docsetutil.
First of all, you need to go to many lines of console output and look for warnings, perhaps there are. Also find the generated docset and right-click> Show Content. If you do not see a lot of html files with documentation, the same thing: you were not able to create the documentation, and docsetutil has nothing to do. And by the way, this is the docsetutil that CoreData uses, it doesn't matter whether you use it in your project or not.
I do not understand why Apple does not provide a tool more sensitive to an oxygen tool. Or it's better to format the code than Crustify. Just take the damn tools and improve them a bit. Argh!
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