code: def set_palette_name(self, palette_name):
          
          combo = self.get_widget('palette_name')
          found = False
          log.debug("wanting palette: %r", palette_name)
          for i in combo.get_model():
              if i[0] == palette_name:
                  combo.set_active_iter(i.iter)
                  found = True
                  break
          if not found:
              combo.set_active(self.custom_palette_index)
docs: If the given palette matches an existing one, shows it in the
          combobox