ZipFileStorage: error handling improvements

src/jio.storage/zipfilestorage.js

@@ -164,7 +164,7 @@
     return loadZip(this)
       .push(function (zip) {
         if (id !== "" && !(zip.files.hasOwnProperty(id) && zip.files[id].dir)) {
-          throw new jIO.util.jIOError("Cannot find document", 404);
+          throw new jIO.util.jIOError("Cannot access subdocument", 404);
         }
         zip.file(attachId, blob);
         return {};
@@ -191,7 +191,7 @@
         }
         if (!(zip.files.hasOwnProperty(attachId) && !zip.files[attachId].dir)) {
           throw new jIO.util.jIOError("Cannot find attachment: "
-            + id + " , " + name,
+            + '/' + id + " , " + name,
             404);
         }
         return zip.file(attachId).async('blob');
@@ -209,7 +209,7 @@
         }
         if (!(zip.files.hasOwnProperty(attachId) && !zip.files[attachId].dir)) {
           throw new jIO.util.jIOError("Cannot find attachment: "
-            + id + " , " + name,
+            + '/' + id + " , " + name,
             404);
         }
         zip.remove(attachId);