Fix is_disconnect to handle closed connection errors

Enhanced is_disconnect() to catch databricks.sql.exc.Error (base class)
and detect "closed connection" errors. This fixes pool_pre_ping failing
when attempting to ping a closed connection.

The default do_ping() tries to create a cursor, which raises Error with
message "Cannot create cursor from closed connection" on closed connections.
Now properly detects this as a disconnect error.

Fixes:
- test_pool_pre_ping_with_closed_connection
- test_is_disconnect_handles_runtime_errors

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: msrathore-db

src/databricks/sqlalchemy/base.py

@@ -357,7 +357,7 @@ def is_disconnect(self, e, connection, cursor):
         Returns:
             True if the error indicates a disconnect, False otherwise
         """
-        from databricks.sql.exc import InterfaceError, DatabaseError
+        from databricks.sql.exc import InterfaceError, DatabaseError, Error
 
         # InterfaceError: Client-side errors (e.g., connection already closed)
         if isinstance(e, InterfaceError):
@@ -368,6 +368,15 @@ def is_disconnect(self, e, connection, cursor):
             error_msg = str(e).lower()
             return "invalid" in error_msg and "handle" in error_msg
 
+        # Base Error class: Check for closed connection errors
+        # This catches errors like "Cannot create cursor from closed connection"
+        if isinstance(e, Error):
+            error_msg = str(e).lower()
+            return (
+                "closed" in error_msg
+                or "cannot create cursor" in error_msg
+            )
+
         return False
 
     @reflection.cache