CAMEL-4396, XSLT exceptions are not logged anymore on System.err.
Unfortunately, the XsltErrorHandler which was introduced does not behave as the default ErrorHandler which logs on System.err and re-throws exceptions (my mistake).
The XsltErrorHandler should re-throw exceptions for ERROR or FATAL, otherwise they are ignored and the service is allowed to start, although the XSLT transformation is not successfully started.
Here is a small patch that fixes that.
The test "XsltTestErrorListenerTest" is still successful.