Avoid a potential NameError (#12789)

adamtheturtle · web-flow · commit f807729ae506 · 2024-08-16T10:45:24.000+01:00
diff --git a/sphinx/util/parallel.py b/sphinx/util/parallel.py
@@ -23,7 +23,7 @@
 logger = logging.getLogger(__name__)
 
 # our parallel functionality only works for the forking Process
-parallel_available = multiprocessing and os.name == 'posix'
+parallel_available = HAS_MULTIPROCESSING and os.name == 'posix'
 
 
 class SerialTasks:
