xclip и xsel — FileNotFoundError: [Errno 2]

У меня есть kivy 1.10.1, python 3.8.2, и я программирую на Ubuntu20.04. Когда я запускаю свою маленькую программу, я получаю эту ошибку:

    [CRITICAL] [Cutbuffer   ] Unable to find any valuable Cutbuffer provider.
xclip - FileNotFoundError: [Errno 2] Aucun fichier ou dossier de ce type: 'xclip'
  File "/usr/lib/python3/dist-packages/kivy/core/__init__.py", line 55, in core_select_lib
    mod = __import__(name='{2}.{0}.{1}'.format(
  File "/usr/lib/python3/dist-packages/kivy/core/clipboard/clipboard_xclip.py", line 17, in <module>
    p = subprocess.Popen(['xclip', '-version'], stdout=subprocess.PIPE)
  File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1702, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)

xsel - FileNotFoundError: [Errno 2] Aucun fichier ou dossier de ce type: 'xsel'
  File "/usr/lib/python3/dist-packages/kivy/core/__init__.py", line 55, in core_select_lib
    mod = __import__(name='{2}.{0}.{1}'.format(
  File "/usr/lib/python3/dist-packages/kivy/core/clipboard/clipboard_xsel.py", line 16, in <module>
    p = subprocess.Popen(['xsel'], stdout=subprocess.PIPE)
  File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1702, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)

Как я могу это исправить, пожалуйста?