[pygobject] tests: avoid mapping a GtkWindow

[Christoph Reiter <creiter src gnome org>]

commit b7d504c3ef689a79448c9f6597ae59153a77104f
Author: Christoph Reiter <creiter src gnome org>
Date:   Sat Apr 1 18:11:46 2017 +0200

    tests: avoid mapping a GtkWindow
    
    This let to a window being shown when running the test suite.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780812

 tests/test_overrides_gdk.py |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/tests/test_overrides_gdk.py b/tests/test_overrides_gdk.py
index 4aff2eb..d671670 100644
--- a/tests/test_overrides_gdk.py
+++ b/tests/test_overrides_gdk.py
@@ -119,7 +119,8 @@ class TestGdk(unittest.TestCase):
         b = Gtk.Button()
         b.connect('button-press-event', button_press_cb)
         w.add(b)
-        w.show_all()
+        b.show()
+        b.realize()
         Gdk.test_simulate_button(b.get_window(),
                                  2, 5,
                                  0,