Merge pull request #7559 from minrk/wait-for-kernel-selector

wait for new-notebook button to arrive

IPython/html/tests/util.js

@@ -13,6 +13,7 b' casper.open_new_notebook = function () {'
     var baseUrl = this.get_notebook_server();
     this.start(baseUrl);
     this.waitFor(this.page_loaded);
+    this.waitForSelector('#kernel-python2 a, #kernel-python3 a');
     this.thenClick('#kernel-python2 a, #kernel-python3 a');
     
     this.waitForPopup('');