about dialog: no need for a specific file for it.

data/ui/about_dialog.ui.in

@@ -2,7 +2,7 @@
 <!-- Generated with glade 3.22.0 -->
 <interface>
   <requires lib="gtk+" version="3.22"/>
-  <template class="AboutDialog" parent="GtkAboutDialog">
+  <object class="GtkAboutDialog" id="about_dialog">
     <property name="can_focus">False</property>
     <property name="type_hint">dialog</property>
     <property name="program_name">Authenticator</property>
@@ -45,5 +45,5 @@ Tobias Bernard</property>
     <child type="titlebar">
       <placeholder/>
     </child>
-  </template>
+  </object>
 </interface>

src/Authenticator/application.py.in

@@ -19,7 +19,7 @@
 from gettext import gettext as _
 from gi.repository import Gtk, GLib, Gio, Gdk, GObject
 
-from Authenticator.widgets import Window, WindowState, AboutDialog, import_json, export_json
+from Authenticator.widgets import Window, WindowState, import_json, export_json
 from Authenticator.models import Database, Settings, Clipboard, Logger, Keyring
 
 
@@ -164,7 +164,9 @@ class Application(Gtk.Application):
         """
             Shows about dialog
         """
-        dialog = AboutDialog()
+        builder = Gtk.Builder()
+        builder.add_from_resource("/com/github/bilelmoussaoui/Authenticator/about_dialog.ui")
+        dialog = builder.get_object("about_dialog")
         dialog.set_transient_for(Window.get_default())
         dialog.run()
         dialog.destroy()

src/Authenticator/widgets/__init__.py

@@ -16,7 +16,6 @@
  You should have received a copy of the GNU General Public License
  along with Authenticator. If not, see <http://www.gnu.org/licenses/>.
 """
-from .about import AboutDialog
 from .accounts import AccountsList, AccountRow
 from .window import Window, WindowState
 from .settings import SettingsWindow

src/Authenticator/widgets/about.py

@@ -1,33 +0,0 @@
-"""
- Copyright © 2017 Bilal Elmoussaoui <bil.elmoussaoui@gmail.com>
-
- This file is part of Authenticator.
-
- Authenticator is free software: you can redistribute it and/or
- modify it under the terms of the GNU General Public License as published
- by the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- Authenticator is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with Authenticator. If not, see <http://www.gnu.org/licenses/>.
-"""
-from gi.repository import Gtk
-
-
-@Gtk.Template(resource_path='/com/github/bilelmoussaoui/Authenticator/about_dialog.ui')
-class AboutDialog(Gtk.AboutDialog):
-    """
-        AboutDialog Widget.
-    """
-    __gtype_name__ ="AboutDialog"
-
-    def __init__(self):
-        super(AboutDialog, self).__init__()
-
-    def __repr__(self):
-        return '<AboutDialog>'