mistralai[patch]: Surface http errors (#20555)

Do not swallow errors when streaming with httpx.

Update affected code if this PR gets merged to httpx:
https://github.com/florimondmanca/httpx-sse/pull/25/files

libs/partners/mistralai/langchain_mistralai/chat_models.py

@@ -116,11 +116,38 @@ def _convert_mistral_chat_message_to_message(
     )
 
 
+def _raise_on_error(response: httpx.Response) -> None:
+    """Raise an error if the response is an error."""
+    if httpx.codes.is_error(response.status_code):
+        error_message = response.read().decode("utf-8")
+        raise httpx.HTTPStatusError(
+            f"Error response {response.status_code} "
+            f"while fetching {response.url}: {error_message}",
+            request=response.request,
+            response=response,
+        )
+
+
+async def _araise_on_error(response: httpx.Response) -> None:
+    """Raise an error if the response is an error."""
+    if httpx.codes.is_error(response.status_code):
+        error_message = (await response.aread()).decode("utf-8")
+        raise httpx.HTTPStatusError(
+            f"Error response {response.status_code} "
+            f"while fetching {response.url}: {error_message}",
+            request=response.request,
+            response=response,
+        )
+
+
 async def _aiter_sse(
     event_source_mgr: AsyncContextManager[EventSource],
 ) -> AsyncIterator[Dict]:
     """Iterate over the server-sent events."""
     async with event_source_mgr as event_source:
+        # TODO(Team): Remove after this is fixed in httpx dependency
+        # https://github.com/florimondmanca/httpx-sse/pull/25/files
+        await _araise_on_error(event_source._response)
         async for event in event_source.aiter_sse():
             if event.data == "[DONE]":
                 return
@@ -144,10 +171,10 @@ async def acompletion_with_retry(
             event_source = aconnect_sse(
                 llm.async_client, "POST", "/chat/completions", json=kwargs
             )
-
             return _aiter_sse(event_source)
         else:
             response = await llm.async_client.post(url="/chat/completions", json=kwargs)
+            await _araise_on_error(response)
             return response.json()
 
     return await _completion_with_retry(**kwargs)
@@ -298,6 +325,9 @@ class ChatMistralAI(BaseChatModel):
                     with connect_sse(
                         self.client, "POST", "/chat/completions", json=kwargs
                     ) as event_source:
+                        # TODO(Team): Remove after this is fixed in httpx dependency
+                        # https://github.com/florimondmanca/httpx-sse/pull/25/files
+                        _raise_on_error(event_source._response)
                         for event in event_source.iter_sse():
                             if event.data == "[DONE]":
                                 return
@@ -305,7 +335,9 @@ class ChatMistralAI(BaseChatModel):
 
                 return iter_sse()
             else:
-                return self.client.post(url="/chat/completions", json=kwargs).json()
+                response = self.client.post(url="/chat/completions", json=kwargs)
+                _raise_on_error(response)
+                return response.json()
 
         rtn = _completion_with_retry(**kwargs)
         return rtn