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

eamanu · Fidget-Spinner · web-flow · commit 24dbe30f8df8 · 2021-09-18T00:58:20.000+02:00
Previous wording didn't explain the slightly unintuitive behavior.

Co-authored-by: kj &lt;28750310+Fidget-Spinner@users.noreply.github.com&gt;
diff --git 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`
