[Matplotlib-users] Error in atexit._run_exitfuncs

[<kei...@bt...>]

I am running matplotlib 1.3.1 under Ubuntu 13 and python3.
Everything works fine, but I get this message every time:

  Error in atexit._run_exitfuncs:  
  AttributeError: 'FigureManagerGTK3Cairo' object has no attribute 'canvas'

What does it mean, and how do I stop it?

Keith