add ConnectionRefusedError raising

bittensor/core/subtensor.py

@@ -186,6 +186,7 @@ def __init__(
 
         self.log_verbose = log_verbose
         self._connection_timeout = connection_timeout
+        self.substrate: "SubstrateInterface" = None
         self._get_substrate()
 
     def __str__(self) -> str:
@@ -201,7 +202,8 @@ def __repr__(self) -> str:
 
     def close(self):
         """Cleans up resources for this subtensor instance like active websocket connection and active extensions."""
-        self.substrate.close()
+        if self.substrate:
+            self.substrate.close()
 
     def _get_substrate(self):
         """Establishes a connection to the Substrate node using configured parameters."""
@@ -223,14 +225,15 @@ def _get_substrate(self):
             except (AttributeError, TypeError, socket.error, OSError) as e:
                 logging.warning(f"Error setting timeout: {e}")
 
-        except ConnectionRefusedError:
+        except ConnectionRefusedError as error:
             logging.error(
                 f"Could not connect to {self.network} network with {self.chain_endpoint} chain endpoint.",
             )
             logging.info(
                 "You can check if you have connectivity by running this command: nc -vz localhost "
-                f"{self.chain_endpoint.split(':')[2]}"
+                f"{self.chain_endpoint}"
             )
+            raise ConnectionRefusedError(error.args)
 
     @staticmethod
     def config() -> "Config":