출처 : https://community.letsencrypt.org/t/pip-error-with-certbot-auto/88200/5

I confirm that it works.
I changed in certbot-auto:
pip_version = StrictVersion(check_output([python, '-m', 'pip', '--version'])
by
pip_version = StrictVersion(check_output(['pip', '--version'])

and
command = [python, '-m', 'pip', 'install', '--no-index', '--no-deps', '-U']
by
command = ['pip', 'install', '--no-index', '--no-deps', '-U']