Issue #16903: Popen.communicate() on Unix now accepts strings when
universal_newlines is true as on Windows.
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index fc456a1..b4adc02 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -537,9 +537,10 @@
.. method:: Popen.communicate(input=None)
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 byte string to be sent to the child process, or
- ``None``, if no data should be sent to the child.
+ until end-of-file is reached. Wait for process to terminate. The optional
+ *input* argument should be data to be sent to the child process, or
+ ``None``, if no data should be sent to the child. The type of *input*
+ must be bytes or, if *universal_newlines* was ``True``, a string.
:meth:`communicate` returns a tuple ``(stdoutdata, stderrdata)``.