Nope, that's a misunderstanding on your part I'm afraid. The "prolog" in that error message/SO question refers to an XML prolog, which is the part in an SGML/XM

Nope, that's a misunderstanding on your part I'm afraid. The "prolog" in that error message/SO question refers to an XML prolog, which is the part in an SGML/XML document up to the first content element ie. an XML declaration and a DTD, both optional.