не удается добавить sudo add-apt-repository ppa: kubuntu-ppa / backports в ubuntu 16.04 [дубликат]

Я пытаюсь установить kubuntu в мю ubuntu 16.04 .

когда я набираю sudo add-apt-repository ppa: kubuntu-ppa / backports

, терминал ничего не показывает. через несколько секунд, когда я нажимаю CTRL + C , терминал выводит следующую ошибку

    falcon@falcon:~$ sudo add-apt-repository ppa:kubuntu-ppa/backports
^CTraceback (most recent call last):
  File "/usr/bin/add-apt-repository", line 122, in <module>
    shortcut = shortcut_handler(line)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 864, in shortcut_handler
    ret = factory(shortcut)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 407, in shortcut_handler
    return PPAShortcutHandler(shortcut)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 364, in __init__
    info = get_ppa_info(self.shortcut)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 335, in get_ppa_info
    ret = get_ppa_info_from_lp(user, ppa)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 92, in get_ppa_info_from_lp
    return get_info_from_lp(lp_url)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 88, in get_info_from_lp
    return _get_https_content_py3(lp_url)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 110, in _get_https_content_py3
    lp_page = urllib.request.urlopen(request, cafile=LAUNCHPAD_PPA_CERT)
  File "/usr/lib/python3.5/urllib/request.py", line 163, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.5/urllib/request.py", line 466, in open
    response = self._open(req, data)
  File "/usr/lib/python3.5/urllib/request.py", line 484, in _open
    '_open', req)
  File "/usr/lib/python3.5/urllib/request.py", line 444, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.5/urllib/request.py", line 1297, in https_open
    context=self._context, check_hostname=self._check_hostname)
  File "/usr/lib/python3.5/urllib/request.py", line 1254, in do_open
    h.request(req.get_method(), req.selector, req.data, headers)
  File "/usr/lib/python3.5/http/client.py", line 1106, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib/python3.5/http/client.py", line 1151, in _send_request
    self.endheaders(body)
  File "/usr/lib/python3.5/http/client.py", line 1102, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python3.5/http/client.py", line 934, in _send_output
    self.send(msg)
  File "/usr/lib/python3.5/http/client.py", line 877, in send
    self.connect()
  File "/usr/lib/python3.5/http/client.py", line 1252, in connect
    super().connect()
  File "/usr/lib/python3.5/http/client.py", line 849, in connect
    (self.host,self.port), self.timeout, self.source_address)
  File "/usr/lib/python3.5/socket.py", line 702, in create_connection
    sock.connect(sa)

РЕДАКТИРОВАТЬ:

У меня такая же ошибка в другом PPA, кажется, это связано с менеджером PPA

PS: Я попробовали несколько вопросов, связанных с этим, но это не решило мою проблему, поэтому начал новый протектор.

ЛЮБОЕ ИСПРАВЛЕНИЕ Пожалуйста. Заранее спасибо