Brett Meyer commented on an issue
Hibernate ORM / Bug HHH-8509
malformed LOG.tracef() throws exception
The first LOG.tracef() in org.hibernate.jpa.boot.internal.PersistenceXmlParser#parsePersistenceXml(URL) throws java.util.MissingFormatArgumentException: Format specifier 's'

The plus must be changed into a comma as the attached patch shows.