Issue 20438: Add a note about deprecating old inspect APIs to whatsnew.

Also, deprecate formatargspec, formatargvalues, and getargvalues
functions.  Since we are deprecating 'getfullargspec' function in
3.5 (documentation only, no DeprecationWarning), it makes sense
to also deprecate functions designed to be directly used with it.

In 3.6 we will remove 'getargsspec' function (was deprecated since
Python 3.0), and start raising DeprecationWarnings in other
'getarg*' family of functions.  We can remove them in 3.7 or later.

Also, it is worth noting, that Signature API does not provide 100%
of functionality that deprecated APIs have.  It is important to do
a soft deprecation of outdated APIs in 3.5 to gather users feedback,
and improve Signature object.

Doc/library/inspect.rst

@@ -793,8 +793,10 @@ Classes and functions
    *n* elements listed in *args*.
 
    .. deprecated:: 3.0
-      Use :func:`getfullargspec` instead, which provides information about
-      keyword-only arguments and annotations.
+      Use :func:`signature` and
+      :ref:`Signature Object <inspect-signature-object>`, which provide a
+      better introspecting API for callables.  This function will be removed
+      in Python 3.6.
 
 
 .. function:: getfullargspec(func)
@@ -834,6 +836,11 @@ Classes and functions
    are the names of the ``*`` and ``**`` arguments or ``None``.  *locals* is the
    locals dictionary of the given frame.
 
+   .. deprecated:: 3.5
+      Use :func:`signature` and
+      :ref:`Signature Object <inspect-signature-object>`, which provide a
+      better introspecting API for callables.
+
 
 .. function:: formatargspec(args[, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations[, formatarg, formatvarargs, formatvarkw, formatvalue, formatreturns, formatannotations]])
 
@@ -856,6 +863,11 @@ Classes and functions
    >>> formatargspec(*getfullargspec(f))
    '(a: int, b: float)'
 
+   .. deprecated:: 3.5
+      Use :func:`signature` and
+      :ref:`Signature Object <inspect-signature-object>`, which provide a
+      better introspecting API for callables.
+
 
 .. function:: formatargvalues(args[, varargs, varkw, locals, formatarg, formatvarargs, formatvarkw, formatvalue])
 
@@ -863,6 +875,11 @@ Classes and functions
    :func:`getargvalues`.  The format\* arguments are the corresponding optional
    formatting functions that are called to turn names and values into strings.
 
+   .. deprecated:: 3.5
+      Use :func:`signature` and
+      :ref:`Signature Object <inspect-signature-object>`, which provide a
+      better introspecting API for callables.
+
 
 .. function:: getmro(cls)
 

Doc/whatsnew/3.5.rst

@@ -815,6 +815,16 @@ Deprecated Python modules, functions and methods
   :meth:`inspect.Signature.from_callable` instead. (Contributed by Yury
   Selivanov in :issue:`24248`.)
 
+* :func:`inspect.getargspec` is deprecated and scheduled to be removed in
+  Python 3.6.  (See :issue:`20438` for details.)
+
+* :func:`~inspect.getfullargspec`, :func:`~inspect.getargvalues`,
+  :func:`~inspect.getcallargs`, :func:`~inspect.getargvalues`,
+  :func:`~inspect.formatargspec`, and :func:`~inspect.formatargvalues` are
+  deprecated in favor of :func:`inspect.signature` API.  (See :issue:`20438`
+  for details.)
+
+
 Deprecated functions and types of the C API
 -------------------------------------------