I am trying to draw an xkcd-style plot with matplotlib (ver. 1.4.2) under Python 3.

When I try to run:

```
import matplotlib.pyplot as plt
plt.xkcd()
plt.plot([1,2,3,4], [1,4,9,16], 'bo')
plt.axis([0, 6, 0, 20])
plt.show()

```

It opens an empty window without any image and I get the error:

```
/usr/lib/python3/dist-packages/matplotlib/font_manager.py:1279: UserWarning: findfont: Font family ['Humor Sans', 'Comic Sans MS', 'StayPuft'] not found. Falling back to Bitstream Vera Sans
  (prop.get_family(), self.defaultFamily[fontext]))
/usr/lib/python3/dist-packages/matplotlib/font_manager.py:1289: UserWarning: findfont: Could not match :family=Bitstream Vera Sans:style=normal:variant=normal:weight=normal:stretch=normal:size=medium. Returning /usr/share/matplotlib/mpl-data/fonts/ttf/STIXSizOneSymReg.ttf
  UserWarning) Exception in Tkinter callback

```

I have Humor Sans installed. I checked it with `fc-list | grep Humor`. It can also be used within other programs, like Libre Office. I also have staypuft installed. Isn't that enough?

The same code above but without the plt.xkcd() bit works flawlessly. 

An alternative to plt.show(), like pylab.savefig() won't work either for the xkcd code, but doesn't have any problem with the same code without using xkcd.