[pygobject] Fix raising an error in a constructor

[Garrett Regier <gregier src gnome org>]

commit 9d0c43b2b9f92fff4249e4eb296f00ea73b15af3
Author: Garrett Regier <Garrett Regier riftio com>
Date:   Thu Aug 7 12:06:30 2014 -0400

    Fix raising an error in a constructor
    
    It should raise a Python exception instead of warnings about
    a constructor returning NULL.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=727004

 gi/pygi-cache.c  |    6 +++---
 tests/test_gi.py |    6 ++++++
 2 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/gi/pygi-cache.c b/gi/pygi-cache.c
index 1682890..4727570 100644
--- a/gi/pygi-cache.c
+++ b/gi/pygi-cache.c
@@ -859,10 +859,10 @@ _constructor_cache_invoke_real (PyGIFunctionCache *function_cache,
                                        py_args, py_kwargs);
     Py_DECREF (py_args);
 
-    if (cache->return_cache == NULL || cache->return_cache->is_skipped)
+    if (ret == NULL || cache->return_cache->is_skipped)
         return ret;
 
-    if (ret != NULL && ret != Py_None) {
+    if (ret != Py_None) {
         if (!PyTuple_Check (ret))
             return ret;
 
@@ -872,7 +872,7 @@ _constructor_cache_invoke_real (PyGIFunctionCache *function_cache,
 
     PyErr_SetString (PyExc_TypeError, "constructor returned NULL");
 
-    Py_XDECREF (ret);
+    Py_DECREF (ret);
     return NULL;
 }
 
diff --git a/tests/test_gi.py b/tests/test_gi.py
index edd8ca0..2c850a7 100644
--- a/tests/test_gi.py
+++ b/tests/test_gi.py
@@ -2111,6 +2111,12 @@ class TestPythonGObject(unittest.TestCase):
         object_ = self.Object(int=42)
         self.assertTrue(isinstance(object_, self.Object))
 
+    @unittest.skipUnless(hasattr(GIMarshallingTests.Object, 'new_fail'),
+                         'Requires newer version of GI')
+    def test_object_fail(self):
+        with self.assertRaises(GLib.Error):
+            GIMarshallingTests.Object.new_fail(int_=42)
+
     def test_object_method(self):
         self.Object(int=0).method()