'In some strange cases we\'re getting:
Error: invalid matrix (not invertible)
This issue was not fixed up-stream, so we\'re applying this ugly patch
that avoids users from getting a crash (but will most likely show an
empty widget).
I don\'t care much about this bug since it only appears once every 6
months or so in my issue tracker.
:see: https://github.com/andresriancho/w3af/issues/726
:see: https://github.com/jrfonseca/xdot.py/issues/1'

def do_expose_event(self, event):

    try:
        return DotWidget.do_expose_event(self, event)
    except cairo.Error:
        pass
