[pygobject] GValue.get_value: fix crashes for Variants

[Christoph Reiter <creiter src gnome org>]

commit 62b16247b9230a975d85e749da9f1b199fbc3c84
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Nov 25 13:13:38 2018 +0100

    GValue.get_value: fix crashes for Variants
    
    g_value_get_variant is transfer-none but was annotated as full which
    results in the bindings unreffing it too many times.
    
    Work around the issue by using g_value_dup_variant instead which is
    really transfer-full.

 gi/overrides/GObject.py         | 4 +++-
 tests/test_overrides_gobject.py | 7 ++++---
 2 files changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/gi/overrides/GObject.py b/gi/overrides/GObject.py
index e6f5b882..a89ddc7d 100644
--- a/gi/overrides/GObject.py
+++ b/gi/overrides/GObject.py
@@ -333,7 +333,9 @@ class Value(GObjectModule.Value):
         elif gtype == TYPE_GTYPE:
             return self.get_gtype()
         elif gtype == TYPE_VARIANT:
-            return self.get_variant()
+            # get_variant was missing annotations
+            # https://gitlab.gnome.org/GNOME/glib/merge_requests/492
+            return self.dup_variant()
         elif gtype == _gi.TYPE_INVALID:
             return None
         else:
diff --git a/tests/test_overrides_gobject.py b/tests/test_overrides_gobject.py
index b902564f..37292dbb 100644
--- a/tests/test_overrides_gobject.py
+++ b/tests/test_overrides_gobject.py
@@ -183,13 +183,14 @@ def test_value_variant():
     assert v.get_value() is None
     variant = GLib.Variant('i', 42)
     v.set_value(variant)
-
-    # FIXME: triggers an assert
-    # assert v.get_value() == variant
+    assert v.get_value() == variant
 
     v.set_value(None)
     assert v.get_value() is None
 
+    with pytest.raises(TypeError):
+        v.set_value(object())
+
 
 def test_value_param():
     # FIXME: set_value and get_value trigger a critical