Invalid display variable: Matplotlib issue with Jupyter

[Wabbit]

I was getting the following error when running the mnist_demo notebook.

136 display = os.environ.get('DISPLAY')
137 if display is None or not re.search(':\d', display):
--> 138 raise RuntimeError('Invalid DISPLAY variable')
139
140 qApp = QtWidgets.QApplication([str(" ")])

RuntimeError: Invalid DISPLAY variable

The solution is to use magic:
%matplotlib inline