[indexeddb] return a jIOError in case of connection error

src/jio.storage/indexeddbstorage.js

@@ -147,8 +147,11 @@
             (error.target instanceof IDBOpenDBRequest) &&
             ((error.target.error instanceof DOMError) ||
              (error.target.error instanceof DOMException))) {
-          reject("Connection to: " + db_name + " failed: " +
-                 error.target.error.message);
+          reject(new jIO.util.jIOError(
+            "Connection to: " + db_name + " failed: " +
+              error.target.error.message,
+            500
+          ));
         } else {
           reject(error);
         }

test/jio.storage/indexeddbstorage.tests.js

@@ -196,11 +196,13 @@
 
   test("version decrease", function () {
     var context = this;
-    expect(1);
+    expect(3);
 
     return setupDBMigrationTest(context, {version: 3},
-                                {version: 2}, function (msg) {
-        ok(startsWith(msg, "Connection to: jio:qunit failed: "));
+                                {version: 2}, function (error) {
+        ok(error instanceof jIO.util.jIOError);
+        equal(error.status_code, 500);
+        ok(startsWith(error.message, "Connection to: jio:qunit failed: "));
       });
   });