weakref: treat explicit None callback as no callback (#8298)

Lib/test/test_weakref.py

@@ -380,7 +380,6 @@ class ReferencesTestCase(TestBase):
     # was not honored, and was broken in different ways for
     # PyWeakref_NewRef() and PyWeakref_NewProxy().  (Two tests.)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_shared_ref_without_callback(self):
         self.check_shared_without_callback(weakref.ref)
 

crates/vm/src/builtins/weakref.rs

@@ -49,7 +49,7 @@ impl Constructor for PyWeak {
         let referent = positional
             .next()
             .ok_or_else(|| vm.new_type_error("__new__ expected at least 1 argument, got 0"))?;
-        let callback = positional.next();
+        let callback = positional.next().filter(|callback| !vm.is_none(callback));
         if let Some(_extra) = positional.next() {
             let got = positional.count() + 3;
             return Err(