Emit deprecation warning for array typecode u (#7157)

Lib/test/test_array.py

@@ -1255,7 +1255,6 @@ class UnicodeTest(StringTest, unittest.TestCase):
         self.assertRaises(ValueError, a.tounicode)
         self.assertRaises(ValueError, str, a)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: DeprecationWarning not triggered
     def test_typecode_u_deprecation(self):
         with self.assertWarns(DeprecationWarning):
             array.array("u")

crates/stdlib/src/array.rs

@@ -35,6 +35,7 @@ mod array {
                 SaturatedSlice, SequenceIndex, SequenceIndexOp, SliceableSequenceMutOp,
                 SliceableSequenceOp,
             },
+            stdlib::warnings,
             types::{
                 AsBuffer, AsMapping, AsSequence, Comparable, Constructor, IterNext, Iterable,
                 PyComparisonOp, Representable, SelfIter,
@@ -645,6 +646,15 @@ mod array {
                 return Err(vm.new_type_error("array.array() takes no keyword arguments"));
             }
 
+            if spec == 'u' {
+                warnings::warn(
+                    vm.ctx.exceptions.deprecation_warning,
+                    "The 'u' type code is deprecated and will be removed in Python 3.16".to_owned(),
+                    1,
+                    vm,
+                )?;
+            }
+
             let mut array =
                 ArrayContentType::from_char(spec).map_err(|err| vm.new_value_error(err))?;