bitbake: lib/ui/taskexp: Fix missing Gtk import

Adding back gtk objects import.

Fix bug introduce when adding validation on gtk import.

(Bitbake rev: 765be5ef60668f8a1cfbcba248f4995725807196)

Signed-off-by: David Khouya <dakhouya@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/ui/taskexp.py

@@ -12,6 +12,7 @@ import sys
 try:
     import gi
     gi.require_version('Gtk', '3.0')
+    from gi.repository import Gtk, Gdk, GObject
 except ValueError:
     sys.exit("FATAL: Gtk version needs to be 3.0")
 except ImportError: