Test failures with OpenSSH 9.8p1

Hi all,

I've noticed two consistent test failures in GNU Guix's diffoscope when building using OpenSSH 9.8p1. Here's the failures:

=================================== FAILURES ===================================
__________________________________ test_diff ___________________________________

differences = []

    @skip_unless_tool_is_at_least("ssh-keygen", openssh_version, "6.9")
    def test_diff(differences):
        expected_diff = get_data("openssh_pub_key_expected_diff")
>       assert differences[0].unified_diff == expected_diff
E       IndexError: list index out of range

tests/comparators/test_openssh_pub_key.py:60: IndexError
__________________________ test_compare_non_existing ___________________________

monkeypatch = <_pytest.monkeypatch.MonkeyPatch object at 0x7fffefa9c700>
opensshpubkey1 = <<class 'abc.PublicKeyFile'> /tmp/guix-build-diffoscope-269.drv-0/source/tests/data/test_openssh_pub_key1.pub>

    @skip_unless_tools_exist("ssh-keygen")
    def test_compare_non_existing(monkeypatch, opensshpubkey1):
        monkeypatch.setattr(Config(), "new_file", True)
        difference = opensshpubkey1.compare(
            MissingFile("/nonexisting", opensshpubkey1)
        )
        assert difference.source2 == "/nonexisting"
>       assert len(difference.details) > 0
E       assert 0 > 0
E        +  where 0 = len([])
E        +    where [] = <Difference /tmp/guix-build-diffoscope-269.drv-0/source/tests/data/test_openssh_pub_key1.pub -- /nonexisting []>.details

tests/comparators/test_openssh_pub_key.py:70: AssertionError

It's possible this is a GNU Guix issue (opened here), although I would be surprised as the breaking commit 6522f93ed0 only upgraded OpenSSH from 9.7p1 to 9.8p1. The issue also occurs in diffoscope 271.