Issue #19698: Remove exec_module() from the built-in and extension module loaders. Due to the fact that the call signatures for extension modules and built-in modules does not allow for the specifying of what module to initialize and that on Windows all extension modules are built-in modules, work to clean up built-in and extension module initialization will have to wait until Python 3.5. Because of this the semantics of exec_module() would be incorrect, so removing the methods for now is the best option; load_module() is still used as a fallback by importlib and so this won't affect semantics.