Tests failing on the S390 architecture, probably because it is big endian

[EdwardBetts]

Tests are failing on the S390 architecture. I think it might be because the S390 architecture is big endian.

The tests pass against the plain Python version of the library without the Cython bit.

$ xvfb-run -a dbus-launch python3.10 -m pytest --no-cov tests -x
==================================================================================== test session starts ====================================================================================
platform linux -- Python 3.10.8, pytest-7.1.2, pluggy-1.0.0+repack -- /usr/bin/python3.10
cachedir: .pytest_cache
rootdir: /home/edward/src/dbus-fast-1.71.0, configfile: pyproject.toml
plugins: cov-4.0.0, asyncio-0.19.0
asyncio: mode=strict
collected 99 items                                                                                                                                                                          

tests/test_address_parser.py::test_valid_addresses PASSED                                                                                                                             [  1%]
tests/test_aio_low_level.py::test_standard_interfaces FAILED                                                                                                                          [  2%]

========================================================================================= FAILURES ==========================================================================================
_________________________________________________________________________________ test_standard_interfaces __________________________________________________________________________________

    @pytest.mark.asyncio
    async def test_standard_interfaces():
>       bus = await MessageBus().connect()

tests/test_aio_low_level.py:9: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
dbus_fast/aio/message_bus.py:234: in connect
    return await future
dbus_fast/aio/message_bus.py:213: in on_hello
    raise err
src/dbus_fast/aio/message_reader.py:24: in dbus_fast.aio.message_reader.build_message_reader._message_reader
    ???
src/dbus_fast/_private/unmarshaller.py:621: in dbus_fast._private.unmarshaller.Unmarshaller._unmarshall
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

>   ???
E   dbus_fast.errors.InvalidMessageError: got unknown protocol version: 0

src/dbus_fast/_private/unmarshaller.py:515: InvalidMessageError
================================================================================== short test summary info ==================================================================================
FAILED tests/test_aio_low_level.py::test_standard_interfaces - dbus_fast.errors.InvalidMessageError: got unknown protocol version: 0
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
================================================================================ 1 failed, 1 passed in 0.12s ================================================================================
$ 

[bdraco]

I definitely expect its because its big endian. Unfortunately I don't have access to any big endian systems to be able to replicate the issue.