Add comment to explain the throws line

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@23151 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/rendition/executer/AbstractTransformationRenderingEngine.java

@@ -58,6 +58,7 @@ public abstract class AbstractTransformationRenderingEngine extends AbstractRend
         // Actually perform the rendition.
         if (null == transformer)
         {
+            // There's no transformer available for the requested rendition!
             throw new RenditionServiceException(String.format(TRANSFORMER_NOT_EXISTS_MESSAGE_PATTERN, sourceMimeType,
                         targetMimeType));
         }