xml: report the filename (if any) when parsing files

A generic "failed to parse xml document" message without telling us
which XML file failed is quite unhelpful.

Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/util/virxml.c

@@ -847,7 +847,8 @@ virXMLParseHelper(int domcode,
 
     if (virGetLastErrorCode() == VIR_ERR_OK) {
         virGenericReportError(domcode, VIR_ERR_XML_ERROR,
-                              "%s", _("failed to parse xml document"));
+                              _("failed to parse xml document '%s'"),
+                              filename ? filename : "[inline data]");
     }
     goto cleanup;
 }