Message Title

If an error occurs during connection creation, an UnknownServiceException can be thrown if the JdbcServices implementation hasn't been registered yet. This hides the actual exception in BasicConnectionCreator.convertSqlException:

org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.engine.jdbc.spi.JdbcServices]
	at app//org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:212)
	at app//org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator.convertSqlException(BasicConnectionCreator.java:121)
	at app//org.hibernate.engine.jdbc.connections.internal.DriverConnectionCreator.makeConnection(DriverConnectionCreator.java:43)
	at app//org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator.createConnection(BasicConnectionCreator.java:61)

The simplest solution seems to be to make UnknownServiceException extend ServiceException (instead of HibernateException).