> New changeset 877df851c3ecdb55306840e247596e7b7805a60a by Mark Shannon in branch 'master':
> bpo-42246: Partial implementation of PEP 626. (GH-23113)

This change introduced reference leaks:
https://buildbot.python.org/all/#builders/384/builds/100

5 tests failed:
    test_asyncgen test_builtin test_coroutines test_exceptions
    test_syntax

For example:

$ ./python -m test test_syntax -R 3:3 -m test.test_syntax.SyntaxTestCase.test_no_indent
0:00:00 load avg: 1.59 Run tests sequentially
0:00:00 load avg: 1.59 [1/1] test_syntax
beginning 6 repetitions
123456
......
test_syntax leaked [27, 27, 27] references, sum=81
test_syntax leaked [20, 20, 20] memory blocks, sum=60
test_syntax failed

== Tests result: FAILURE ==

1 test failed:
    test_syntax

Total duration: 955 ms
Tests result: FAILURE