python-starlette fails to build with Python 3.13.0b1.

___________________________ test_debug_html[asyncio] ___________________________

test_client_factory = functools.partial(<class 'starlette.testclient.TestClient'>, backend='asyncio', backend_options={})

    def test_debug_html(test_client_factory: TestClientFactory) -> None:
        async def app(scope: Scope, receive: Receive, send: Send) -> None:
            raise RuntimeError("Something went wrong")
    
        app = ServerErrorMiddleware(app, debug=True)
        client = test_client_factory(app, raise_server_exceptions=False)
        response = client.get("/", headers={"Accept": "text/html, */*"})
        assert response.status_code == 500
>       assert response.headers["content-type"].startswith("text/html")

tests/middleware/test_errors.py:53: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = Headers({}), key = 'content-type'

    def __getitem__(self, key: str) -> str:
        """
        Return a single header value.
    
        If there are multiple headers with the same key, then we concatenate
        them with commas. See: https://tools.ietf.org/html/rfc7230#section-3.2.2
        """
        normalized_key = key.lower().encode(self.encoding)
    
        items = [
            header_value.decode(self.encoding)
            for _, header_key, header_value in self._list
            if header_key == normalized_key
        ]
    
        if items:
            return ", ".join(items)
    
>       raise KeyError(key)
E       KeyError: 'content-type'

/usr/lib/python3.13/site-packages/httpx/_models.py:228: KeyError
____________________________ test_debug_html[trio] _____________________________

test_client_factory = functools.partial(<class 'starlette.testclient.TestClient'>, backend='trio', backend_options={})

    def test_debug_html(test_client_factory: TestClientFactory) -> None:
        async def app(scope: Scope, receive: Receive, send: Send) -> None:
            raise RuntimeError("Something went wrong")
    
        app = ServerErrorMiddleware(app, debug=True)
        client = test_client_factory(app, raise_server_exceptions=False)
        response = client.get("/", headers={"Accept": "text/html, */*"})
        assert response.status_code == 500
>       assert response.headers["content-type"].startswith("text/html")

tests/middleware/test_errors.py:53: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = Headers({}), key = 'content-type'

    def __getitem__(self, key: str) -> str:
        """
        Return a single header value.
    
        If there are multiple headers with the same key, then we concatenate
        them with commas. See: https://tools.ietf.org/html/rfc7230#section-3.2.2
        """
        normalized_key = key.lower().encode(self.encoding)
    
        items = [
            header_value.decode(self.encoding)
            for _, header_key, header_value in self._list
            if header_key == normalized_key
        ]
    
        if items:
            return ", ".join(items)
    
>       raise KeyError(key)
E       KeyError: 'content-type'

/usr/lib/python3.13/site-packages/httpx/_models.py:228: KeyError
___________ test_gzip_ignored_for_responses_with_encoding_set[trio] ____________

cls = <class '_pytest.runner.CallInfo'>
func = <function call_runtest_hook.<locals>.<lambda> at 0x7f0fd00a2840>
when = 'call'
reraise = (<class '_pytest.outcomes.Exit'>, <class 'KeyboardInterrupt'>)

    @classmethod
    def from_call(
        cls,
        func: "Callable[[], TResult]",
        when: "Literal['collect', 'setup', 'call', 'teardown']",
        reraise: Optional[
            Union[Type[BaseException], Tuple[Type[BaseException], ...]]
        ] = None,
    ) -> "CallInfo[TResult]":
        """Call func, wrapping the result in a CallInfo.
    
        :param func:
            The function to call. Called without arguments.
        :param when:
            The phase in which the function is called.
        :param reraise:
            Exception or exceptions that shall propagate if raised by the
            function, instead of being wrapped in the CallInfo.
        """
        excinfo = None
        start = timing.time()
        precise_start = timing.perf_counter()
        try:
>           result: Optional[TResult] = func()

/usr/lib/python3.13/site-packages/_pytest/runner.py:341: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python3.13/site-packages/_pytest/runner.py:262: in <lambda>
    lambda: ihook(item=item, **kwds), when=when, reraise=reraise
/usr/lib/python3.13/site-packages/pluggy/_hooks.py:493: in __call__
    return self._hookexec(self.name, self._hookimpls, kwargs, firstresult)
/usr/lib/python3.13/site-packages/pluggy/_manager.py:115: in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
/usr/lib/python3.13/site-packages/_pytest/unraisableexception.py:88: in pytest_runtest_call
    yield from unraisable_exception_runtest_hook()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    def unraisable_exception_runtest_hook() -> Generator[None, None, None]:
        with catch_unraisable_exception() as cm:
            yield
            if cm.unraisable:
                if cm.unraisable.err_msg is not None:
                    err_msg = cm.unraisable.err_msg
                else:
                    err_msg = "Exception ignored in"
                msg = f"{err_msg}: {cm.unraisable.object!r}\n\n"
                msg += "".join(
                    traceback.format_exception(
                        cm.unraisable.exc_type,
                        cm.unraisable.exc_value,
                        cm.unraisable.exc_traceback,
                    )
                )
>               warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))
E               pytest.PytestUnraisableExceptionWarning: Exception ignored in: <gzip on 0x7f0fd0276380>
E               
E               Traceback (most recent call last):
E                 File "/usr/lib64/python3.13/gzip.py", line 359, in close
E                   fileobj.write(self.compress.flush())
E                   ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
E               ValueError: I/O operation on closed file.

/usr/lib/python3.13/site-packages/_pytest/unraisableexception.py:78: PytestUnraisableExceptionWarning
=========================== short test summary info ============================

https://docs.python.org/3.13/whatsnew/3.13.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.13-b1/fedora-rawhide-x86_64/07532355-python-starlette/

For all our attempts to build python-starlette with Python 3.13, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.13-b1/package/python-starlette/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.13:
https://copr.fedorainfracloud.org/coprs/g/python/python3.13-b1/

Let us know here if you have any questions.

Python 3.13 is planned to be included in Fedora 41.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.13.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.