Rendering in Jupyter Lab issue for 0.24.0
After installing 0.24.0, I have seen the behavior screen-shot below across several of my existing Jupyter Lab notebooks, when trying to call `df.head()`. Along with the error message, it still renders a version of the dataframe, but not the nice formatting expected.

![image](https://user-images.githubusercontent.com/8319226/51850387-a575ce00-22ef-11e9-9f38-457dd17465e4.png)
