bpo-33594: Add deprecation info in inspect.py module (GH-7036)

(cherry picked from commit ded87d804e2a85b2a3ea9e7a11384b41fafdfa29)

Co-authored-by: Matthias Bussonnier <bussonniermatthias@gmail.com>
diff --git a/Lib/inspect.py b/Lib/inspect.py
index b5d583c..da4a424 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1070,8 +1070,10 @@
     Alternatively, use getfullargspec() for an API with a similar namedtuple
     based interface, but full support for annotations and keyword-only
     parameters.
+
+    Deprecated since Python 3.5, use `inspect.getfullargspec()`.
     """
-    warnings.warn("inspect.getargspec() is deprecated, "
+    warnings.warn("inspect.getargspec() is deprecated since Python 3.0, "
                   "use inspect.signature() or inspect.getfullargspec()",
                   DeprecationWarning, stacklevel=2)
     args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, ann = \
@@ -2802,19 +2804,25 @@
 
     @classmethod
     def from_function(cls, func):
-        """Constructs Signature for the given python function."""
+        """Constructs Signature for the given python function.
 
-        warnings.warn("inspect.Signature.from_function() is deprecated, "
-                      "use Signature.from_callable()",
+        Deprecated since Python 3.5, use `Signature.from_callable()`.
+        """
+
+        warnings.warn("inspect.Signature.from_function() is deprecated since "
+                      "Python 3.5, use Signature.from_callable()",
                       DeprecationWarning, stacklevel=2)
         return _signature_from_function(cls, func)
 
     @classmethod
     def from_builtin(cls, func):
-        """Constructs Signature for the given builtin function."""
+        """Constructs Signature for the given builtin function.
 
-        warnings.warn("inspect.Signature.from_builtin() is deprecated, "
-                      "use Signature.from_callable()",
+        Deprecated since Python 3.5, use `Signature.from_callable()`.
+        """
+
+        warnings.warn("inspect.Signature.from_builtin() is deprecated since "
+                      "Python 3.5, use Signature.from_callable()",
                       DeprecationWarning, stacklevel=2)
         return _signature_from_builtin(cls, func)