Apply @rwgk's fixes to cherry-picked commits from pybind#2392

Author: YannickJadoul

tests/test_pytypes.py

@@ -111,13 +111,14 @@ def __repr__(self):
     assert s1 == s2
 
     malformed_utf8 = b"\x80"
+    assert m.str_from_object(malformed_utf8) is malformed_utf8  # To be fixed; see #2380
     if env.PY2:
+        # with pytest.raises(UnicodeDecodeError):
+        #     m.str_from_object(malformed_utf8)
         with pytest.raises(UnicodeDecodeError):
-            assert m.str_from_object(malformed_utf8)
-        with pytest.raises(UnicodeDecodeError):
-            assert m.str_from_handle(malformed_utf8)
+            m.str_from_handle(malformed_utf8)
     else:
-        assert m.str_from_object(malformed_utf8) == "b'\\x80'"
+        # assert m.str_from_object(malformed_utf8) == "b'\\x80'"
         assert m.str_from_handle(malformed_utf8) == "b'\\x80'"