[hibernate-dev] Can't build Hibernate ORM 5.1 documentation

I'm getting ready to release 5.1.17, but I'm having trouble building the documentation. I can't even build the documentation using 5.1.16 tag. It worked fine when I released 5.1.16.Final in August. A new property was added for HHH-13011, and I need to get that documented in the user guide for 5.1.17. Here is what I'm seeing when I execute `./gradlew buildDocs`: :documentation:renderDocBook_mappingGuide_en-US_html rendering Book(mappingGuide) en-US/html Extending script classloader with the jdocbookXsl dependencies redirecting console output to file [/home/gbadner/git/hibernate-orm-5.1-copy/documentation/target/docbook/work/mappingGuide/log/console-en-US-html.log] Error on line 1 column 1 of http://docbook.org/xml/5.0/dtd/docbook.dtd: Error reported by XML parser: The markup declarations contained or pointed to by the document type declaration must be well-formed. Resetting console output :documentation:renderDocBook_mappingGuide_en-US_html FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':documentation:renderDocBook_mappingGuide_en-US_html'. http://docbook.org/xml/5.0/dtd/docbook.dtd; lineNumber: 1; columnNumber: 1; The markup decl arations contained or pointed to by the document type declaration must be well-formed.] on Hibernate_Mapping_Guide.xml The log file (/home/gbadner/git/hibernate-orm-5.1-copy/documentation/target/docbook/work/mappingGuide/log/console-en-US-html.log) was empty. I'm attaching the console log from executing `./gradlew buildDocs --debug --info`. Any ideas??? Thanks, Gail