Issue #25802: Deprecate load_module() on importlib.machinery.SourceFileLoader and SourcelessFileLoader.

They were the only remaining implementations of load_module() not
documented as deprecated.
diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
index c660933..bf5161d 100644
--- a/Doc/whatsnew/3.6.rst
+++ b/Doc/whatsnew/3.6.rst
@@ -189,7 +189,12 @@
 Deprecated Python modules, functions and methods
 ------------------------------------------------
 
-* None yet.
+* :meth:`importlib.machinery.SourceFileLoader` and
+  :meth:`importlib.machinery.SourcelessFileLoader` are now deprecated. They
+  were the only remaining implementations of
+  :meth:`importlib.abc.Loader.load_module` in :mod:`importlib` that had not
+  been deprecated in previous versions of Python in favour of
+  :meth:`importlib.abc.Loader.exec_module`.
 
 
 Deprecated functions and types of the C API