Error not raised in session fixture when mark.xfail is set on last test

[romuald]

Version
6.2.2

Context
Running a test suite with a session fixture that does some cleaning up

Description
If the last test of the suite has a mark.xfail, the error will be marked as an additional xfailed test

Minimal example

import pytest

@pytest.fixture(autouse=True, scope='session')
def failme():
    yield

    raise RuntimeError('cleanup fails for some reason')

def test_01_OK():
    assert 1 == 1

@pytest.mark.xfail()
def test_02_fail():
    assert 0 == 1

% py.test -v test.py
test.py::test_01_OK PASSED
test.py::test_02_fail XFAIL
test.py::test_02_fail XFAIL

To me, it would seem more appropriate to raise the error since the fixture is executed in the context of the session, not the test