bpo-43908: check_set_special_type_attr() checks Py_TPFLAGS_IMMUTABLETYPE (GH-25743)

check_set_special_type_attr() and type_set_annotations()
now check for immutable flag (Py_TPFLAGS_IMMUTABLETYPE).

Co-authored-by: Victor Stinner <vstinner@python.org>
2 files changed