feat(core): trace response body on error (#32653)

libs/core/langchain_core/language_models/chat_models.py

@@ -78,6 +78,11 @@ def _generate_response_from_error(error: BaseException) -> list[ChatGeneration]:
     if hasattr(error, "response"):
         response = error.response
         metadata: dict = {}
+        if hasattr(response, "json"):
+            try:
+                metadata["body"] = response.json()
+            except Exception:
+                metadata["body"] = getattr(response, "text", None)
         if hasattr(response, "headers"):
             try:
                 metadata["headers"] = dict(response.headers)