Gtk.Entry is not receiving editing-done signal (at least in python3, ubuntu 16.04)

[xoristzatziki]

Description: Ubuntu 16.04.4 LTS
Release: 16.04

According to:
https://developer.gnome.org/gtk3/stable/GtkCellEditable.html#GtkCellEditable-editing-done

Implementations of GtkCellEditable are responsible for emitting this signal when they are done editing, e.g. GtkEntry is emitting it when the user presses Enter.

What I did:
On the http://python-gtk-3-tutorial.readthedocs.io/en/latest/entry.html example I added a "connect signal":
        self.entry.connect("editing-done", self.on_editentry_done)

also added the def
    def on_editentry_done(self, widget, *args):
        print('Hi!')

Running the script and pressing either the "enter" or the "return" key, inside the entry box, expected "Hi!" to be printed on the terminal.

(I have not checked if this is not working in C, I checked only in python 3)