3.9
bpo-9216: Add usedforsecurity to hashlib constructors (GH-16044)
bpo-33164: blake2: Fix Coverity scan (GH-25060)
Issue #26798: Add BLAKE2 (blake2b and blake2s) to hashlib.
bpo-40268: Remove explicit pythread.h includes (#19529)
bpo-40024: Update C extension modules to use PyModule_AddType() (GH-19119)