[HUDSON-4941] Log which file had an XML parse error to assist in diagnosis & fix.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@24022 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/XmlFile.java

@@ -147,7 +147,7 @@ public final class XmlFile {
         try {
             return xs.unmarshal(new XppReader(r),o);
         } catch (StreamException e) {
-            throw new IOException2(e);
+            throw new IOException2("Unable to read "+file,e);
         } catch(ConversionException e) {
             throw new IOException2("Unable to read "+file,e);
         } catch(Error e) {// mostly reflection errors