bpo-36760: Clarify subprocess capture_output docs. (GH-13322)

Clarify how to capture stdout and stderr combined into one stream.

diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 3280c95cacbbc36c5f9e021e121e8749ed4add49..d840b461f98cb7c8857ee28f6b16eb6ebaecf690 100644 (file)
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -55,7 +55,9 @@ compatibility with older versions, see the :ref:`call-function-trio` section.
    If *capture_output* is true, stdout and stderr will be captured.
    When used, the internal :class:`Popen` object is automatically created with
    ``stdout=PIPE`` and ``stderr=PIPE``. The *stdout* and *stderr* arguments may
-   not be supplied at the same time as *capture_output*.
+   not be supplied at the same time as *capture_output*.  If you wish to capture
+   and combine both streams into one, use ``stdout=PIPE`` and ``stderr=STDOUT``
+   instead of *capture_output*.
 
    The *timeout* argument is passed to :meth:`Popen.communicate`. If the timeout
    expires, the child process will be killed and waited for.  The