Support for older python

src/calibre/utils/forked_map.py

@@ -9,12 +9,20 @@ import ssl
 import traceback
 from collections.abc import Callable, Iterator
 from contextlib import ExitStack
-from itertools import batched, chain
+from itertools import chain, islice
 from typing import Any, BinaryIO, NamedTuple, TypeVar
 
 T = TypeVar('T')
 R = TypeVar('R')
 
+try:
+    from itertools import batched
+except ImportError:
+    def batched(iterable, n):
+        iterator = iter(iterable)
+        while batch := tuple(islice(iterator, n)):
+            yield batch
+
 
 class _RemoteTraceback(Exception):
     def __init__(self, tb):
@@ -60,7 +68,9 @@ class Worker:
         return self
 
     def __exit__(self, exc_type, exc_value, tb) -> None:
+        try:
             self.pipe.close()
+        finally:
             pid, status = os.waitpid(self.pid, os.WNOHANG)
             if not pid:
                 os.kill(self.pid, signal.SIGKILL)