feat: optimize weaviate error msg (#441)

api/core/index/vector_index/weaviate_vector_index.py

 from typing import Optional, cast
 
+import requests
 import weaviate
 from langchain.embeddings.base import Embeddings
 from langchain.schema import Document, BaseRetriever
@@ -34,12 +35,15 @@ class WeaviateVectorIndex(BaseVectorIndex):
 
         weaviate.connect.connection.has_grpc = False
 
+        try:
             client = weaviate.Client(
                 url=config.endpoint,
                 auth_client_secret=auth_config,
                 timeout_config=(5, 60),
                 startup_period=None
             )
+        except requests.exceptions.ConnectionError:
+            raise ConnectionError("Vector database connection error")
 
         client.batch.configure(
             # `batch_size` takes an `int` value to enable auto-batching