Fix JS test new button selector

IPython/html/tests/util.js

@@ -13,7 +13,8 b' casper.open_new_notebook = function () {'
     var baseUrl = this.get_notebook_server();
     this.start(baseUrl);
     this.waitFor(this.page_loaded);
-    this.thenClick('button#new_notebook');
+    this.thenClick('#kernel-python2 a, #kernel-python3 a');
+    
     this.waitForPopup('');
 
     this.withPopup('', function () {this.waitForSelector('.CodeMirror-code');});