{"action":"closed","issue":{"url":"https://api.github.com/repos/ipython/ipython/issues/8680","labels_url":"https://api.github.com/repos/ipython/ipython/issues/8680/labels{/name}","comments_url":"https://api.github.com/repos/ipython/ipython/issues/8680/comments","events_url":"https://api.github.com/repos/ipython/ipython/issues/8680/events","html_url":"https://github.com/ipython/ipython/issues/8680","id":98559304,"number":8680,"title":"HelloWidget Example- \"No default value found for None trait\" error","user":{"login":"klanea","id":13054486,"avatar_url":"https://avatars.githubusercontent.com/u/13054486?v=3","gravatar_id":"","url":"https://api.github.com/users/klanea","html_url":"https://github.com/klanea","followers_url":"https://api.github.com/users/klanea/followers","following_url":"https://api.github.com/users/klanea/following{/other_user}","gists_url":"https://api.github.com/users/klanea/gists{/gist_id}","starred_url":"https://api.github.com/users/klanea/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/klanea/subscriptions","organizations_url":"https://api.github.com/users/klanea/orgs","repos_url":"https://api.github.com/users/klanea/repos","events_url":"https://api.github.com/users/klanea/events{/privacy}","received_events_url":"https://api.github.com/users/klanea/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":{"login":"jdfreder","id":3292874,"avatar_url":"https://avatars.githubusercontent.com/u/3292874?v=3","gravatar_id":"","url":"https://api.github.com/users/jdfreder","html_url":"https://github.com/jdfreder","followers_url":"https://api.github.com/users/jdfreder/followers","following_url":"https://api.github.com/users/jdfreder/following{/other_user}","gists_url":"https://api.github.com/users/jdfreder/gists{/gist_id}","starred_url":"https://api.github.com/users/jdfreder/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jdfreder/subscriptions","organizations_url":"https://api.github.com/users/jdfreder/orgs","repos_url":"https://api.github.com/users/jdfreder/repos","events_url":"https://api.github.com/users/jdfreder/events{/privacy}","received_events_url":"https://api.github.com/users/jdfreder/received_events","type":"User","site_admin":false},"milestone":null,"comments":2,"created_at":"2015-08-01T20:23:08Z","updated_at":"2015-09-21T18:58:41Z","closed_at":"2015-09-21T18:58:41Z","body":"Hi all,\r\n\r\nI just installed a fresh copy IPython via ``pip install --upgrade \"ipython[all]\"'' on two Debian-based machines and tried to take the \"Custom Widget - Hello World\" notebook for a test run:\r\nhttps://github.com/ipython/ipython/blob/master/examples/Interactive%20Widgets/Custom%20Widget%20-%20Hello%20World.ipynb\r\n\r\nWhen I Run All on both machines, I first get an error on the traitlets import, claiming it's not defined. Looks like traitlets doesn't get installed by default. No problem: sudo pip install traitlets. Unfortunately, both instances then fail when I try to instantiate the widget itself:\r\n\r\n![capture](https://cloud.githubusercontent.com/assets/13054486/9023442/e9e70114-384f-11e5-9181-2062a1bf46a7.PNG)\r\n\r\nI recall this demo used to work fine (last I checked 4-5 months ago). Have changes to traits support on the backend broken this example? Is there a step I'm missing?\r\n\r\nI see at least one recent traits-related bug: https://github.com/jupyter/jupyterhub/issues/262\r\nIs there a connection?\r\n\r\nThanks in advance!"}}