Import GDK in preparation for GTK3 conversion

Some parts of GTK moved to GDK, so we need to import the latter for things to
work after the conversion script runs.

Signed-off-by: Sascha Silbe <silbe@activitycentral.com>

src/sugar3/activity/widgets.py

@@ -15,6 +15,7 @@
 # Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 # Boston, MA 02111-1307, USA.
 
+from gtk import gdk
 import gtk
 import gettext
 import gconf