Fix bug where validation errors don't give any details

src/main/java/com/xmlcalabash/library/ValidateJing.java

@@ -105,7 +105,7 @@ public void run() throws SaxonApiException {
        boolean checkIdRefs = getOption(_dtd_id_idref_warnings,false);
        boolean dtdAugment  = getOption(_dtd_attribute_values,false);

        ErrorHandler eh = new RNGErrorHandler();
        RNGErrorHandler eh = new RNGErrorHandler();
        PropertyMapBuilder properties = new PropertyMapBuilder();
        properties.put(ValidateProperty.ERROR_HANDLER, eh);
        properties.put(ValidateProperty.URI_RESOLVER, runtime.getResolver());
@@ -156,15 +156,15 @@ public void run() throws SaxonApiException {
                InputSource din = S9apiUtils.xdmToInputSource(runtime, doc);
                if (!driver.validate(din)) {
                    if (assertValid) {
                        throw XProcException.stepError(53);
                        throw XProcException.stepError(53, eh.getErr());
                    }
                }
            } else {
                throw new XProcException(step.getNode(), "Error loading schema");
            }
        } catch (SAXParseException e) {
            if (assertValid) {
                throw XProcException.stepError(53);
                throw XProcException.stepError(53, e);
            }
        } catch (SAXException e) {
            throw new XProcException("SAX Exception", e);
@@ -188,6 +188,10 @@ private String compactSchema(XdmNode doc) {
    class RNGErrorHandler implements ErrorHandler {
        SAXParseException err = null;

        public SAXParseException getErr() {
            return err;
        }

        public void fatalError(SAXParseException e) throws SAXException {
            error(e);
        }
@@ -213,7 +217,7 @@ public void error(SAXParseException e) throws SAXException {
            treeWriter.endDocument();

            step.reportError(treeWriter.getResult());
            if (err != null) {
            if (err == null) {
                err = e;
            }
        }

src/main/java/com/xmlcalabash/library/ValidateWithRNG.java

@@ -59,7 +59,7 @@
    private WritablePipe result = null;
    private URI docBaseURI = null;

    /* Creates a new instance of Delete */
    /* Creates a new instance of ValidateWithRNG */
    public ValidateWithRNG(XProcRuntime runtime, XAtomicStep step) {
        super(runtime,step);
    }
@@ -102,7 +102,7 @@ public void run() throws SaxonApiException {
            doc = source.read();
            docBaseURI = doc.getBaseURI();

            if (verifier != null && !verifier.verify(S9apiUtils.xdmToInputSource(runtime, doc))) {
            if (!verifier.verify(S9apiUtils.xdmToInputSource(runtime, doc))) {
                throw new XProcException(XProcException.err_E0001, "Document is not valid");
            }

@@ -113,7 +113,7 @@ public void run() throws SaxonApiException {
        } catch (SAXException sx) {
            // Assume the only error is validity failed?
            if (getOption(_assert_valid,false)) {
                throw XProcException.stepError(53);
                throw XProcException.stepError(53, sx);
            }
            result.write(doc);
        } catch (IOException ioe) {