Changes 54857 and 54840 broke code and were reverted in Py2.5 just before
it was released, but that reversion never made it to the Py2.6 head.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 1035e5f..3b7c128 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1406,7 +1406,7 @@
return -1;
}
mp = (PyDictObject*)a;
- if (PyDict_CheckExact(b)) {
+ if (PyDict_Check(b)) {
other = (PyDictObject*)b;
if (other == mp || other->ma_used == 0)
/* a.update(a) or a.update({}); nothing to do */