ubuntu@ip-172-31-40-141:/$ sudo apt-get install python-pip python-dev build-essential
sudo: /etc/sudoers is world writable
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin
ubuntu@ip-172-31-40-141:/$ sudo chmod o-w /etc/sudoers
sudo: /etc/sudoers is world writable
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin
ubuntu@ip-172-31-40-141:/$ pkexec apt-get purge sudo
==== AUTHENTICATING FOR org.freedesktop.policykit.exec ===
Authentication is needed to run `/usr/bin/apt-get' as the super user
Authenticating as: Ubuntu (ubuntu)
Password: 
polkit-agent-helper-1: pam_authenticate failed: Authentication failure
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized
This incident has been reported.
ubuntu@ip-172-31-40-141:/$ passwd
Changing password for ubuntu.
(current) UNIX password: 
passwd: Authentication token manipulation error
passwd: password unchanged
ubuntu@ip-172-31-40-141:/$ sudo su
sudo: /etc/sudoers is world writable
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin
ubuntu@ip-172-31-40-141:/$ passwd root
passwd: You may not view or modify password information for root.