Made a boo boo in /etc/environment

Soo, you followed a few links, edited the /etc/environment based on 'accepted solution' against best practices and now you cannot login to the VM.

The boo boo made in the file is causing the login screen to loop regardless of the correct password entered (or another issue depending on the edit you did).

Buck up, let's recovery.

Go to recovery mode:
- Press 'Esc' on bootup ('shift' on some machines)
- Select 'Advanced options for Ubuntu'

 - Select 'recovery mode'

 - Select 'root' to get a terminal with permission

Press control-D to continue

  type: 'mount -o rw,remount /'

The above step makes the file editable which is otherwise read-only

Now use nano or vi to edit the file (undo mistake)

Then issue a 'reboot' command.

Hope this fixes your issue!