Now on to the bug. There seems to be a problem in the new colorbar
with the extend keyword in matplotlib version 0.87.3.
The colors/labels on the colorbar are screwed up if I do contourf
plots of arrays in which all of the values are below the minimum
contour or above the maximum contour.
As someone pointed out to me, this bug is squashed in the subversion.
Sorry for clogging up your inboxes.