Try fixing error

dev/flwr_dev/build_docker_image_matrix.py

@@ -20,8 +20,23 @@
 
 import json
 from dataclasses import asdict, dataclass, field
-from enum import StrEnum
-from typing import Any, Callable, Literal, Optional
+
+try:
+    from enum import StrEnum
+
+    class _DistroName(StrEnum):
+        ALPINE = "alpine"
+        UBUNTU = "ubuntu"
+
+except ImportError:
+    from enum import Enum
+
+    class _DistroName(str, Enum):
+        ALPINE = "alpine"
+        UBUNTU = "ubuntu"
+
+
+from typing import Any, Callable, Optional
 
 import typer
 
@@ -32,11 +47,6 @@
 # assert sys.version_info < (3, 11), "Script requires Python 3.9 or lower."
 
 
-class _DistroName(StrEnum):
-    ALPINE = "alpine"
-    UBUNTU = "ubuntu"
-
-
 @dataclass
 class _Distro:
     name: "_DistroName"