Apply PEP 486 changes from Paul Moore

pep-0486.txt

@@ -83,6 +83,7 @@ will always be used (as at present).
 Impact on Script Launching
 ==========================
 
+
 As well as interactive use, the launcher is used as the Windows file
 association for Python scripts.  In that case, a "shebang" (``#!``)
 line at the start of the script is used to identify the interpreter to
@@ -90,26 +91,18 @@ run.  A fully-qualified path can be used, or a version-specific Python
 (``python3`` or ``python2``, or even ``python3.5``), or the generic
 ``python``, which means to use the default interpreter.
 
-With the proposed change, scripts that start with ``#!python`` (or one
+The launcher also looks for the specific shebang line
-of its equivalent forms) will be run using an active virtualenv.  This
+``#!/usr/bin/env python``. On Unix, the ``env`` program searches for a
-is a change in behaviour, although it will only affect users running
+command on ``$PATH`` and runs the command so located. Similarly, with
-scripts from the command line with a virtualenv activated.
+this shebang line, the launcher will look for a copy of ``python.exe``
+on the user's current ``%PATH%`` and will run that copy.
 
-Under Unix, the ``#!/usr/bin/env python`` shebang line will use the
+As activating a virtualenv means that it is added to ``PATH``, no
-version of Python found on ``$PATH``, whereas ``#!/usr/bin/python``
+special handling is needed to run scripts with the active virtualenv -
-will use the system Python.  In order to match Unix behaviour as
+they just need to use the ``#!/usr/bin/env python`` shebang line,
-closely as possible, it is proposed that the two shebang forms::
+exactly as on Unix. (If there is no activated virtualenv, and no
-
+``python.exe`` on ``PATH``, the launcher will look for a default
-    #!/usr/bin/env python
+Python exactly as if the shebang line had said ``#!python``).
-    #!python
-
-use an active virtualenv, if present, whereas the forms::
-
-    #!/usr/bin/python
-    #!/usr/local/bin/python
-
-use *only* the default system Python, and ignore the ``VIRTUAL_ENV``
-environment variable.
 
 
 Exclusions
@@ -126,6 +119,13 @@ dealing with their system Python installations, to be able to continue
 to do so when using virtual environments.
 
 
+Reference Implementation
+========================
+
+A patch implementing the proposed behaviour is available at
+http://bugs.python.org/issue23465
+
+
 References
 ==========