jakevdp/ipywidgets — pull request #14 by mglerner (2014-11-12 15:39:34+00:00)
Title: work around matplotlib bug

In my version of matplotlib (1.4.2 installed via conda), obj._repr_html_() is returning None for matplotlib.figure.Figure objects. So, you divs that just contain "None" and the figures show up later.

This isn't a pretty patch, but it should solve the problem without contaminating anything else that I can see.