sudo
sudo: >>> /etc/sudoers: syntax error near line 56 <<<
sudo: parse error in /etc/sudoers near line 56
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

visudo
visudo: /etc/sudoers: Permission denied
visudo: /etc/sudoers: Permission denied

pkexec visudo
Error executing command as another user: No authentication agent was found.