bpo-37055: fix warnings in _blake2 module (GH-14646)


https://bugs.python.org/issue37055

Automerge-Triggered-By: @tiran
(cherry picked from commit b27cbec801e17a13d7fef49116a8fc279930d2b1)

Co-authored-by: Inada Naoki <songofacandy@gmail.com>
3 files changed