test_append is broken on FreeBSD

[ligurio]

setup_unreliablefs = ('/tmp/pytest-of-root/pytest-0/test_append0/mnt', '/tmp/pytest-of-root/pytest-0/test_append0/src')
    def test_append(setup_unreliablefs):
        mnt_dir, src_dir = setup_unreliablefs
        name = name_generator()
        os_create(pjoin(src_dir, name))
        fullname = pjoin(mnt_dir, name)
        with os_open(fullname, os.O_WRONLY) as fd:
            os.write(fd, b'foo\n')
        with os_open(fullname, os.O_WRONLY|os.O_APPEND) as fd:
>           os.write(fd, b'bar\n')
E           OSError: [Errno 9] Bad file descriptor
tests/test_unreliablefs.py:188: OSError

https://cirrus-ci.com/task/5170998354903040?command=test#L66