bpo-46431: improve error message on invalid calls to BaseExceptionGroup.__new__ (GH-30854)

3 files changed, 6 insertions, 2 deletions

diff --git a/Lib/test/test_exception_group.py b/Lib/test/test_exception_group.py
index f0ae377..bbfce94 100644
--- a/Lib/test/test_exception_group.py
+++ b/Lib/test/test_exception_group.py
@@ -22,7 +22,7 @@ class TestExceptionGroupTypeHierarchy(unittest.TestCase):
 
 class BadConstructorArgs(unittest.TestCase):
     def test_bad_EG_construction__too_many_args(self):
-        MSG = 'function takes exactly 2 arguments'
+        MSG = 'BaseExceptionGroup.__new__\(\) takes exactly 2 arguments'
         with self.assertRaisesRegex(TypeError, MSG):
             ExceptionGroup('no errors')
         with self.assertRaisesRegex(TypeError, MSG):
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-01-24-16-58-01.bpo-46431.N6mKAx.rst b/Misc/NEWS.d/next/Core and Builtins/2022-01-24-16-58-01.bpo-46431.N6mKAx.rst
new file mode 100644
index 0000000..3a2af9d
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-01-24-16-58-01.bpo-46431.N6mKAx.rst
@@ -0,0 +1 @@
+Improve error message on invalid calls to :meth:`BaseExceptionGroup.__new__`.
\ No newline at end of file
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 065503f..d8bfb31 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -685,7 +685,10 @@ BaseExceptionGroup_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     PyObject *message = NULL;
     PyObject *exceptions = NULL;
 
-    if (!PyArg_ParseTuple(args, "UO", &message, &exceptions)) {
+    if (!PyArg_ParseTuple(args,
+                          "UO:BaseExceptionGroup.__new__",
+                          &message,
+                          &exceptions)) {
         return NULL;
     }