Issue #25154: Deprecate the pyvenv script.

This was done so as to move users to `python3 -m venv` which prevents
confusion over which Python interpreter will be used in the virtual
environment when more than one is installed.
diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index b374280..22513cf8 100644
--- a/Doc/whatsnew/3.6.rst
+++ b/Doc/whatsnew/3.6.rst
@@ -197,7 +197,10 @@
 Deprecated features
 -------------------
 
-* None yet.
+* The ``pyvenv`` script has been deprecated in favour of ``python3 -m venv``.
+  This prevents confusion as to what Python interpreter ``pyvenv`` is
+  connected to and thus what Python interpreter will be used by the virtual
+  environment. See :issue:`25154`.
 
 
 Removed
diff --git a/Misc/NEWS b/Misc/NEWS
index 6e3e2c3..7d2c79f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -289,6 +289,12 @@
 
 - Issue #25022: Removed very outdated PC/example_nt/ directory.
 
+Tools/Demos
+-----------
+
+- Issue #25154: The pyvenv script has been deprecated in favour of
+  `python3 -m venv`.
+
 
 What's New in Python 3.5.1 release candidate 1?
 ===============================================
diff --git a/Tools/scripts/pyvenv b/Tools/scripts/pyvenv
index 978d691..1043efc 100755
--- a/Tools/scripts/pyvenv
+++ b/Tools/scripts/pyvenv
@@ -1,6 +1,12 @@
 #!/usr/bin/env python3
 if __name__ == '__main__':
     import sys
+    import pathlib
+
+    executable = pathlib.Path(sys.executable or 'python3').name
+    print('WARNING: the pyenv script is deprecated in favour of '
+          '`{} -m venv`'.format(exeutable, file=sys.stderr))
+
     rc = 1
     try:
         import venv