do not allow _PyGen_Finalize to fail (closes #27811)

Patch from Armin Rigo.
diff --git a/Objects/genobject.c b/Objects/genobject.c
index b3e0a46..a9ea5c2 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -24,18 +24,6 @@
     PyObject *res;
     PyObject *error_type, *error_value, *error_traceback;
 
-    /* If `gen` is a coroutine, and if it was never awaited on,
-       issue a RuntimeWarning. */
-    if (gen->gi_code != NULL
-            && ((PyCodeObject *)gen->gi_code)->co_flags & CO_COROUTINE
-            && gen->gi_frame != NULL
-            && gen->gi_frame->f_lasti == -1
-            && !PyErr_Occurred()
-            && PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
-                                "coroutine '%.50S' was never awaited",
-                                gen->gi_qualname))
-        return;
-
     if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
         /* Generator isn't paused, so no need to close */
         return;
@@ -43,7 +31,20 @@
     /* Save the current exception, if any. */
     PyErr_Fetch(&error_type, &error_value, &error_traceback);
 
-    res = gen_close(gen, NULL);
+    /* If `gen` is a coroutine, and if it was never awaited on,
+       issue a RuntimeWarning. */
+    if (gen->gi_code != NULL
+            && ((PyCodeObject *)gen->gi_code)->co_flags & CO_COROUTINE
+            && gen->gi_frame->f_lasti == -1
+            && !PyErr_Occurred()
+            && PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
+                                "coroutine '%.50S' was never awaited",
+                                gen->gi_qualname)) {
+        res = NULL;  /* oops, exception */
+    }
+    else {
+        res = gen_close(gen, NULL);
+    }
 
     if (res == NULL)
         PyErr_WriteUnraisable(self);