Improve error handling in st.write_stream (streamlit#8036)

* Improve error handling in write stream

* Add spaces

* Remove import

* Update error text

lib/streamlit/elements/write.py

@@ -14,7 +14,6 @@
 
 from __future__ import annotations
 
-import contextlib
 import dataclasses
 import inspect
 import json as json
@@ -203,14 +202,30 @@ def flush_stream_response():
             if type_util.is_type(
                 chunk, "openai.types.chat.chat_completion_chunk.ChatCompletionChunk"
             ):
-                # Try to convert openai chat completion chunk to a string:
-                with contextlib.suppress(Exception):
+                # Try to convert OpenAI chat completion chunk to a string:
+                try:
                     chunk = chunk.choices[0].delta.content or ""
+                except AttributeError as err:
+                    raise StreamlitAPIException(
+                        "Failed to parse the OpenAI ChatCompletionChunk. "
+                        "The most likely cause is a change of the chunk object structure "
+                        "due to a recent OpenAI update. You might be able to fix this "
+                        "by downgrading the OpenAI library or upgrading Streamlit. Also, "
+                        "please report this issue to: https://github.com/streamlit/streamlit/issues."
+                    ) from err
 
             if type_util.is_type(chunk, "langchain_core.messages.ai.AIMessageChunk"):
-                # Try to convert langchain_core message chunk to a string:
-                with contextlib.suppress(Exception):
+                # Try to convert LangChain message chunk to a string:
+                try:
                     chunk = chunk.content or ""
+                except AttributeError as err:
+                    raise StreamlitAPIException(
+                        "Failed to parse the LangChain AIMessageChunk. "
+                        "The most likely cause is a change of the chunk object structure "
+                        "due to a recent LangChain update. You might be able to fix this "
+                        "by downgrading the OpenAI library or upgrading Streamlit. Also, "
+                        "please report this issue to: https://github.com/streamlit/streamlit/issues."
+                    ) from err
 
             if isinstance(chunk, str):
                 first_text = False