Lightsail "sudo: no valid sudoers sources found, quitting"

I FIXED IT! You basically build an instance from a snapshot, but add a launch script which runs as root to change the permissions on your sudoers file. Then you can edit sudoers as a non root user. Then you make another snapshot instance with another launch script that sets the permissions back to normal.

1. create a snapshot of your instance
2. create a new instance from the snapshot, but click on the +Add Launch Script
3. add the following launch script: chmod 777 /etc/sudoers
4. Connnect to the instance and modify your sudoers file back too normal (you may have to wait a few seconds for the launch script to apply the permission change)
5. reboot
6. create a snapshot of the instance
7. create another instance from the new snapshot, click on +Add Launch Script
8. add the following launch script: chmod 440 /etc/sudoers
9. Connect to the instance and test sudo -s (you may have to wait again for the launch script to apply the permission change)
10. Detach IP from original instance. Attach to new instance
11. Reset all firewall rules
12. Delete other instances