Traceback (most recent call last):
  File "/usr/share/alacarte/Alacarte/MainWindow.py", line 626, in on_properties_button_clicked
    self.on_edit_properties_activate(None)
  File "/usr/share/alacarte/Alacarte/MainWindow.py", line 377, in on_edit_properties_activate
    open(file_path, 'w').write(data)
IOError: [Errno 13] Permission denied: '/home/username/.local/share/applications/firefox.desktop'