[Bug #1575506] The _singlefileMailbox class was using the wrong file object in its flush() method, causing an error
diff --git a/Misc/NEWS b/Misc/NEWS
index 13f52a7..64fa7bf 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -105,6 +105,9 @@
- Bug #1565661: in webbrowser, split() the command for the default
GNOME browser in case it is a command with args.
+- Bug #1575506: Single-file mailboxes didn't re-lock properly in
+ their flush() method.
+
- Bug #1576241: fix functools.wraps() to work on built-in functions.
- Fix a bug in traceback.format_exception_only() that led to an error