[doc] Clarify exception in `multiprocessing.cpu_count` (GH-23660) (GH-28433)

Previous wording didn't explain the slightly unintuitive behavior.

Co-authored-by: kj <28750310+Fidget-Spinner@users.noreply.github.com>
(cherry picked from commit 24dbe30f8df80740704db3743d071b3218d1276e)

Co-authored-by: Emmanuel Arias <eamanu@yaerobi.com>

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 945ac42b2fbb37992e4fda0370e6d6eb8dabbc55..57df89951e332c4efd896e47e978fd13b4730bc5 100644 (file)
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -951,7 +951,8 @@ Miscellaneous
    use.  The number of usable CPUs can be obtained with
    ``len(os.sched_getaffinity(0))``
 
-   May raise :exc:`NotImplementedError`.
+   When the number of CPUs cannot be determined a :exc:`NotImplementedError`
+   is raised.
 
    .. seealso::
       :func:`os.cpu_count`