Issue #13597: Fix the documentation of the "-u" command-line option, and wording of "What's new in Python 3.0" about standard streams.
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index c73f1e0..9274d8e 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -247,7 +247,8 @@
Force the binary layer of the stdin, stdout and stderr streams (which is
available as their ``buffer`` attribute) to be unbuffered. The text I/O
- layer will still be line-buffered.
+ layer will still be line-buffered if writing to the console, or
+ block-buffered if redirected to a non-interactive file.
See also :envvar:`PYTHONUNBUFFERED`.