Issue #27285: Document the deprecation of the pyvenv script.

As part of the update, the documentation was updated to normalize
around the term "virtual environment" instead of relying too heavily
on "venv" for the same meaning and leading to inconsistent usage of
either.

Thanks to Steve Piercy for the patch.
diff --git a/Doc/installing/index.rst b/Doc/installing/index.rst
index 1ef3149..b22465d 100644
--- a/Doc/installing/index.rst
+++ b/Doc/installing/index.rst
@@ -2,9 +2,9 @@
 
 .. _installing-index:
 
-*****************************
-  Installing Python Modules
-*****************************
+*************************
+Installing Python Modules
+*************************
 
 :Email: distutils-sig@python.org
 
@@ -34,24 +34,24 @@
 
 * ``pip`` is the preferred installer program. Starting with Python 3.4, it
   is included by default with the Python binary installers.
-* a virtual environment is a semi-isolated Python environment that allows
+* A *virtual environment* is a semi-isolated Python environment that allows
   packages to be installed for use by a particular application, rather than
-  being installed system wide
-* ``pyvenv`` is the standard tool for creating virtual environments, and has
+  being installed system wide.
+* ``venv`` is the standard tool for creating virtual environments, and has
   been part of Python since Python 3.3. Starting with Python 3.4, it
-  defaults to installing ``pip`` into all created virtual environments
+  defaults to installing ``pip`` into all created virtual environments.
 * ``virtualenv`` is a third party alternative (and predecessor) to
-  ``pyvenv``. It allows virtual environments to be used on versions of
-  Python prior to 3.4, which either don't provide ``pyvenv`` at all, or
+  ``venv``. It allows virtual environments to be used on versions of
+  Python prior to 3.4, which either don't provide ``venv`` at all, or
   aren't able to automatically install ``pip`` into created environments.
-* the `Python Packaging Index <https://pypi.python.org/pypi>`__ is a public
+* The `Python Packaging Index <https://pypi.python.org/pypi>`__ is a public
   repository of open source licensed packages made available for use by
-  other Python users
+  other Python users.
 * the `Python Packaging Authority
   <https://www.pypa.io/en/latest/>`__ are the group of
   developers and documentation authors responsible for the maintenance and
   evolution of the standard packaging tools and the associated metadata and
-  file format standards. They maintain a variety of tools, documentation
+  file format standards. They maintain a variety of tools, documentation,
   and issue trackers on both `GitHub <https://github.com/pypa>`__ and
   `BitBucket <https://bitbucket.org/pypa/>`__.
 * ``distutils`` is the original build and distribution system first added to
@@ -62,6 +62,19 @@
   of the mailing list used to coordinate Python packaging standards
   development).
 
+.. deprecated:: 3.6
+   ``pyvenv`` was the recommended tool for creating virtual environments for
+   Python 3.3 and 3.4, and is `deprecated in Python 3.6
+   <https://docs.python.org/dev/whatsnew/3.6.html#deprecated-features>`_.
+
+.. versionchanged:: 3.5
+   The use of ``venv`` is now recommended for creating virtual environments.
+
+.. seealso::
+
+   `Python Packaging User Guide: Creating and using virtual environments
+   <https://packaging.python.org/installing/#creating-virtual-environments>`__
+
 
 Basic usage
 ===========
@@ -100,13 +113,14 @@
 More information and resources regarding ``pip`` and its capabilities can be
 found in the `Python Packaging User Guide <https://packaging.python.org>`__.
 
-``pyvenv`` has its own documentation at :ref:`scripts-pyvenv`. Installing
-into an active virtual environment uses the commands shown above.
+Creation of virtual environments is done through the :mod:`venv` module.
+Installing packages into an active virtual environment uses the commands shown
+above.
 
 .. seealso::
 
     `Python Packaging User Guide: Installing Python Distribution Packages
-    <https://packaging.python.org/en/latest/installing/>`__
+    <https://packaging.python.org/installing/>`__
 
 
 How do I ...?
@@ -124,7 +138,7 @@
 .. seealso::
 
    `Python Packaging User Guide: Requirements for Installing Packages
-   <https://packaging.python.org/en/latest/installing/#requirements-for-installing-packages>`__
+   <https://packaging.python.org/installing/#requirements-for-installing-packages>`__
 
 
 .. installing-per-user-installation:
@@ -142,20 +156,19 @@
 A number of scientific Python packages have complex binary dependencies, and
 aren't currently easy to install using ``pip`` directly. At this point in
 time, it will often be easier for users to install these packages by
-`other means
-<https://packaging.python.org/en/latest/science/>`__
+`other means <https://packaging.python.org/science/>`__
 rather than attempting to install them with ``pip``.
 
 .. seealso::
 
    `Python Packaging User Guide: Installing Scientific Packages
-   <https://packaging.python.org/en/latest/science/>`__
+   <https://packaging.python.org/science/>`__
 
 
 ... work with multiple versions of Python installed in parallel?
 ----------------------------------------------------------------
 
-On Linux, Mac OS X and other POSIX systems, use the versioned Python commands
+On Linux, Mac OS X, and other POSIX systems, use the versioned Python commands
 in combination with the ``-m`` switch to run the appropriate copy of
 ``pip``::
 
@@ -164,7 +177,7 @@
    python3   -m pip install SomePackage  # default Python 3
    python3.4 -m pip install SomePackage  # specifically Python 3.4
 
-(appropriately versioned ``pip`` commands may also be available)
+Appropriately versioned ``pip`` commands may also be available.
 
 On Windows, use the ``py`` Python launcher in combination with the ``-m``
 switch::
@@ -212,11 +225,11 @@
 than needing to build them themselves.
 
 Some of the solutions for installing `scientific software
-<https://packaging.python.org/en/latest/science/>`__
-that is not yet available as pre-built ``wheel`` files may also help with
+<https://packaging.python.org/science/>`__
+that are not yet available as pre-built ``wheel`` files may also help with
 obtaining other binary extensions without needing to build them locally.
 
 .. seealso::
 
    `Python Packaging User Guide: Binary Extensions
-   <https://packaging.python.org/en/latest/extensions/>`__
+   <https://packaging.python.org/extensions/>`__