Use empty redis db for tests (#751)

* Tests should only run on empty Redis databases

* Minor ruff fixes

* Minor cleanups

Author: selwin

tests/redis_config.py

@@ -1,8 +1,7 @@
 from __future__ import annotations
 
-import os
+from collections.abc import Sequence
 from dataclasses import dataclass
-from typing import Sequence
 
 from redis import Redis
 from redis.exceptions import RedisError
@@ -22,10 +21,6 @@ def _find_empty_databases(host: str, port: int, *, required: int) -> Sequence[in
     Raises RuntimeError if we cannot connect or if we cannot find the requested
     number of empty databases. Sentinel ports are intentionally not probed.
     """
-    # try:
-    #     redis = Redis(host=host, port=port, db=0)
-    # except Exception as exc:  # pragma: no cover - defensive guard
-    #     raise RuntimeError(f"Refusing to run tests: cannot connect to Redis at {host}:{port}") from exc
 
     empty_databases: list[int] = []