Fix Context.new_bytes (#6989)

Lib/test/test_ast/test_ast.py

@@ -2663,7 +2663,6 @@ class ConstantTests(unittest.TestCase):
         self.assertEqual(str(cm.exception),
                          "got an invalid type in Constant: list")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; b'' is not b''
     def test_singletons(self):
         for const in (None, False, True, Ellipsis, b''):
             with self.subTest(const=const):

crates/vm/src/vm/context.rs

@@ -455,7 +455,11 @@ impl Context {
 
     #[inline]
     pub fn new_bytes(&self, data: Vec<u8>) -> PyRef<PyBytes> {
-        PyBytes::from(data).into_ref(self)
+        if data.is_empty() {
+            self.empty_bytes.clone()
+        } else {
+            PyBytes::from(data).into_ref(self)
+        }
     }
 
     #[inline]