Print warning if DiskCache when RedisCache requested (microsoft#1921)

Author: jackgerrits

autogen/cache/cache_factory.py

@@ -1,7 +1,9 @@
-from typing import Optional, Union, Type
+from typing import Optional, Union
 from .abstract_cache_base import AbstractCache
 from .disk_cache import DiskCache
 
+import logging
+
 
 class CacheFactory:
     @staticmethod
@@ -45,6 +47,7 @@ def cache_factory(
 
                 return RedisCache(seed, redis_url)
             except ImportError:
+                logging.warning("RedisCache is not available. Creating a DiskCache instance instead.")
                 return DiskCache(f"./{cache_path_root}/{seed}")
         else:
             return DiskCache(f"./{cache_path_root}/{seed}")