console.error when using unknown attributes in templates.

sky/tests/framework/templates.sky

 <sky>
 <import src="/sky/tests//resources/chai.sky" />
 <import src="/sky/tests/resources/mocha.sky" />
 <import src="/sky/tests/resources/test-element.sky" as="TestElement" />
 
 <div id="sandbox"></div>
 
 <test-element id="parser-element" checked="true" size="10" name="foo bar" />
 
 <script>
@@ skipping 102 matching lines @@
     assert.isTrue(isNaN(element.size));
     element.size = {};
     assert.isTrue(isNaN(element.size));
   });
 
   it("should connect data binding", function(done) {
     sandbox.appendChild(element);
     var inside = element.shadowRoot.getElementById("inside");
     Promise.resolve().then(function() {
       assert.equal(inside.textContent, 10);
-      assert.equal(inside.attr, 10);
+      assert.equal(inside.lang, 10);
       element.value = 20;
     }).then(function() {
       assert.equal(inside.textContent, 20);
-      assert.equal(inside.attr, 20);
+      assert.equal(inside.lang, 20);
       done();
     }).catch(function(e) {
       done(e);
     });
   });
 
   it("should connect event handlers", function() {
     sandbox.appendChild(element);
     var inside = element.shadowRoot.getElementById("inside");
     inside.dispatchEvent(new CustomEvent("wrong-event"));
     assert.isNull(element.lastEvent);
     var event = new CustomEvent("test-event");
     inside.dispatchEvent(event);
     assert.equal(element.lastEvent, event);
   });
 
   it("should call shadowRootReady after creating the template instance", function() {
     assert.equal(element.shadowRootReadyCount, 0);
     sandbox.appendChild(element);
     assert.equal(element.shadowRootReadyCount, 1);
     element.remove();
     sandbox.appendChild(element);
     assert.equal(element.shadowRootReadyCount, 1);
   });
 });
 </script>
 </sky>