I haven't used docutils itself. It came out while using sphinx. It creates XMLs usingdocutils_xml writer.
Way to reproduce with sphinx 1.2.2 is:
./sphinx-build.py -b xml Python-2.7.6/Doc dest
ran on Python docs source.
As a result it creates beforementioned wrong XMLs:
The error is using attribute key without value, while XML spec forbids it:
Please look at https://bitbucket.org/birkenfeld/sphinx/issue/1450/xml-builder-creates-invalid-xml-file to see example xml line with error, with explanation from sphinx specialist.