bpo-38992: avoid fsum test failure from constant-folding (GH-17513) (GH-17530)

* Issue 38992: avoid fsum test failure

* Add NEWS entry
(cherry picked from commit bba873e633f0f1e88ea12fb935cbd58faa77f976)

Co-authored-by: Mark Dickinson <mdickinson@enthought.com>
2 files changed