add a note about the ftruncate change
diff --git a/Misc/NEWS b/Misc/NEWS
index 8ef9cef..c7be9e0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- os.ftruncate raises OSErrors instead of IOErrors for consistency with other os
+  functions.
+
 - Issue #4991: Passing invalid file descriptors to io.FileIO now raises an
   OSError.