Test TestUserAgent::test_user_agent_header_format fails on a pre-release Python

[musicinmybrain]

On a pre-release Python interpreter version, the test TestUserAgent::test_user_agent_header_format fails. For example, with Python 3.15.0a5:

$ pytest -v -k 'TestUserAgent and test_user_agent_header_format'
=================================================================================== test session starts ====================================================================================
platform linux -- Python 3.15.0a5, pytest-9.0.2, pluggy-1.6.0 -- /home/ben/src/forks/hatch/.venv/bin/python3
cachedir: .pytest_cache
rootdir: /home/ben/src/forks/hatch
configfile: pyproject.toml
plugins: anyio-4.12.1
collected 2259 items / 2258 deselected / 1 selected                                                                                                                                        

tests/index/test_core.py::TestUserAgent::test_user_agent_header_format FAILED [100%]

========================================================================================= FAILURES =========================================================================================
_______________________________________________________________________ TestUserAgent.test_user_agent_header_format ________________________________________________________________________

self = <tests.index.test_core.TestUserAgent object at 0x7f0d343e56d0>

    def test_user_agent_header_format(self):
        index = PackageIndex("https://foo.internal/a/b/")
        client = index.client
    
        user_agent = client.headers["User-Agent"]
    
        expected = (
            f"Hatch/{__version__} {sys.implementation.name}/{platform.python_version()} HTTPX/{httpx.__version__}"
        )
>       assert user_agent == expected
E       AssertionError: assert 'Hatch/1.16.3... HTTPX/0.28.1' == 'Hatch/1.16.3... HTTPX/0.28.1'
E         
E         - Hatch/1.16.3.dev3 cpython/3.15.0a5 HTTPX/0.28.1
E         ?                                 --
E         + Hatch/1.16.3.dev3 cpython/3.15.0 HTTPX/0.28.1

/home/ben/src/forks/hatch/tests/index/test_core.py:86: AssertionError
================================================================================= short test summary info ==================================================================================
FAILED tests/index/test_core.py::TestUserAgent::test_user_agent_header_format - AssertionError: assert 'Hatch/1.16.3... HTTPX/0.28.1' == 'Hatch/1.16.3... HTTPX/0.28.1'
============================================================================ 1 failed, 2258 deselected in 0.61s ============================================================================

It looks like this is a consequence of 8e1a709, specifically 557ed17.

This was first reported downstream in Fedora.