#2683: communicate() takes bytes.

Doc/library/subprocess.rst

@@ -102,7 +102,7 @@ This module defines one class called :class:`Popen`:
 
       This feature is only available if Python is built with universal newline support
       (the default).  Also, the newlines attribute of the file objects :attr:`stdout`,
-      :attr:`stdin` and :attr:`stderr` are not updated by the communicate() method.
+      :attr:`stdin` and :attr:`stderr` are not updated by the :meth:`communicate` method.
 
    The *startupinfo* and *creationflags*, if given, will be passed to the
    underlying CreateProcess() function.  They can specify things such as appearance
@@ -215,7 +215,7 @@ Instances of the :class:`Popen` class have the following methods:
 
    Interact with process: Send data to stdin.  Read data from stdout and stderr,
    until end-of-file is reached.  Wait for process to terminate. The optional
-   *input* argument should be a string to be sent to the child process, or
+   *input* argument should be a byte string to be sent to the child process, or
    ``None``, if no data should be sent to the child.
 
    :meth:`communicate` returns a tuple ``(stdout, stderr)``.