Update mappinproxy's get

Author: jopemachine

Lib/test/test_types.py

@@ -1029,8 +1029,6 @@ def test_get(self):
         self.assertIsNone(view.get('xxx'))
         self.assertEqual(view.get('xxx', 42), 42)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_missing(self):
         class dictmissing(dict):
             def __missing__(self, key):

vm/src/builtins/mappingproxy.rs

@@ -83,9 +83,12 @@ impl PyMappingProxy {
         default: OptionalArg,
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyObjectRef>> {
-        let default = default.into_option();
-        let value = self.get_inner(key, vm)?.or(default);
-        Ok(value)
+        let obj = self.to_object(vm)?;
+        Ok(Some(vm.call_method(
+            &obj,
+            "get",
+            (key, default.unwrap_or_none(vm)),
+        )?))
     }
 
     #[pymethod(magic)]