Seems that commit 933dfd7504e521a27fd8b94d02b79f9ed08f4631 introduced some reference leaks:


commit 933dfd7504e521a27fd8b94d02b79f9ed08f4631
Author: Christian Heimes <christian@python.org>
Date:   Sat Mar 27 14:55:03 2021 +0100

    bpo-40645: use C implementation of HMAC (GH-24920)



𓋹 ./python.exe -m test test_hashlib -R 3:3
0:00:00 load avg: 5.67 Run tests sequentially
0:00:00 load avg: 5.67 [1/1] test_hashlib
beginning 6 repetitions
123456
......
test_hashlib leaked [1, 1, 1] references, sum=3
test_hashlib failed

== Tests result: FAILURE ==

1 test failed:
    test_hashlib

Total duration: 8.7 sec
Tests result: FAILURE


    - [x] fix tests
    - [ ] add test scenarios for old/new code.

    Signed-off-by: Christian Heimes <christian@python.org>

 Lib/hashlib.py                                     |   1 +
 Lib/hmac.py                                        |  86 +++++++-----
 Lib/test/test_hmac.py                              | 114 +++++++++-------
 .../2021-03-19-10-22-17.bpo-40645.5pXhb-.rst       |   2 +
 Modules/_hashopenssl.c                             | 150 +++++++++++++++++++--
 Modules/clinic/_hashopenssl.c.h                    |  38 +-----
 6 files changed, 267 insertions(+), 124 deletions(-)
 create mode 100644 bpo-40645.5pXhb-.rst">Misc/NEWS.d/next/Library/2021-03-19-10-22-17.bpo-40645.5pXhb-.rst