[pygobject] tests: Work around a crash in the new gtk4 a11y stack

[Christoph Reiter <creiter src gnome org>]

commit 8b28e3834f73506a2a32a451670e5bef812b0c5b
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Nov 15 16:48:13 2020 +0100

    tests: Work around a crash in the new gtk4 a11y stack
    
    gtk4 calls get_dbus_object_path() on the default app and glib leaves
    invalid GApplication instances as default in various places. It's hard
    to track where a new default instances gets set, so just disable a11y
    in the test suite for now.

 tests/__init__.py | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/tests/__init__.py b/tests/__init__.py
index e6dd333a..125f2319 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -58,6 +58,10 @@ def init_test_environ():
     # Avoid accessibility dbus warnings
     os.environ['NO_AT_BRIDGE'] = '1'
 
+    # A workaround for https://gitlab.gnome.org/GNOME/glib/-/issues/2251
+    # The gtk4 a11y stack calls get_dbus_object_path() on the default app
+    os.environ['GTK_A11Y'] = 'none'
+
     # Force the default theme so broken themes don't affect the tests
     os.environ['GTK_THEME'] = 'Adwaita'