Rm pytz dep (#6978)

langchain/callbacks/arthur_callback.py

@@ -9,7 +9,6 @@ from time import time
 from typing import TYPE_CHECKING, Any, DefaultDict, Dict, List, Optional, Union
 
 import numpy as np
-import pytz
 
 from langchain.callbacks.base import BaseCallbackHandler
 from langchain.schema import AgentAction, AgentFinish, LLMResult
@@ -162,6 +161,12 @@ class ArthurCallbackHandler(BaseCallbackHandler):
 
     def on_llm_end(self, response: LLMResult, **kwargs: Any) -> None:
         """On LLM end, send data to Arthur."""
+        try:
+            import pytz  # type: ignore[import]
+        except ImportError as e:
+            raise ImportError(
+                "Could not import pytz. Please install it with 'pip install pytz'."
+            ) from e
 
         run_id = kwargs["run_id"]