open() / TextIOWrapper doc: make it explicit than newline='\n' doesn't

translate newlines on output.

Doc/library/functions.rst

@@ -888,9 +888,9 @@ are always available.  They are listed here in alphabetical order.
 
    * On output, if *newline* is ``None``, any ``'\n'`` characters written are
      translated to the system default line separator, :data:`os.linesep`.  If
-     *newline* is ``''``, no translation takes place.  If *newline* is any of
-     the other legal values, any ``'\n'`` characters written are translated to
-     the given string.
+     *newline* is ``''`` or ``'\n'``, no translation takes place.  If *newline*
+     is any of the other legal values, any ``'\n'`` characters written are
+     translated to the given string.
 
    If *closefd* is ``False`` and a file descriptor rather than a filename was
    given, the underlying file descriptor will be kept open when the file is

Doc/library/io.rst

@@ -770,9 +770,9 @@ Text I/O
 
    * On output, if *newline* is ``None``, any ``'\n'`` characters written are
      translated to the system default line separator, :data:`os.linesep`.  If
-     *newline* is ``''``, no translation takes place.  If *newline* is any of
-     the other legal values, any ``'\n'`` characters written are translated to
-     the given string.
+     *newline* is ``''`` or ``'\n'``, no translation takes place.  If *newline*
+     is any of the other legal values, any ``'\n'`` characters written are
+     translated to the given string.
 
    If *line_buffering* is ``True``, :meth:`flush` is implied when a call to
    write contains a newline character.

Modules/_io/_iomodule.c

@@ -264,9 +264,9 @@ PyDoc_STRVAR(open_doc,
 "\n"
 "* On output, if newline is None, any '\\n' characters written are\n"
 "  translated to the system default line separator, os.linesep. If\n"
-"  newline is '', no translation takes place. If newline is any of the\n"
-"  other legal values, any '\\n' characters written are translated to\n"
-"  the given string.\n"
+"  newline is '' or '\n', no translation takes place. If newline is any\n"
+"  of the other legal values, any '\\n' characters written are translated\n"
+"  to the given string.\n"
 "\n"
 "If closefd is False, the underlying file descriptor will be kept open\n"
 "when the file is closed. This does not work when a file name is given\n"

Modules/_io/textio.c

@@ -635,9 +635,9 @@ PyDoc_STRVAR(textiowrapper_doc,
     "\n"
     "* On output, if newline is None, any '\\n' characters written are\n"
     "  translated to the system default line separator, os.linesep. If\n"
-    "  newline is '', no translation takes place. If newline is any of the\n"
-    "  other legal values, any '\\n' characters written are translated to\n"
-    "  the given string.\n"
+    "  newline is '' or '\n', no translation takes place. If newline is any\n"
+    "  of the other legal values, any '\\n' characters written are translated\n"
+    "  to the given string.\n"
     "\n"
     "If line_buffering is True, a call to flush is implied when a call to\n"
     "write contains a newline character."