gtk_selection_data_set_pixbuf fails because PIXMAP != image/png

["Xavier Toth" <txtoth gmail com>]

I'm trying to copy&paste an image using the default clipboard. I'm
using pygtk and retrieving the image from the clipboard using
gtk.Clipboard.wait_for_image then later I try to set the selection
data pixbuf using gtk.SelectionData.set_pixbuf() with the data gotten
from wait_for_image but this fails. Debugging
gtk_selection_data_set_pixbuf I see that the selection data target is
PIXMAP but the mime type of the pixbuf format is 'image/png' and these
don't match so gtk.SelectionData.set_pixbuf() fails. What do I need to
do to get this to work?