Comment 0 for bug 131399

chris@HAL421:~$ sudo visduo
right after Defaults you find the following 2 lines:
# Uncomment to allow members of group sudo to not need a password
#%sudo ALL=NOPASSWD: ALL

Uncomment the sudo line, save the file, make sure you are in the sudo group:
chris@HAL421:~$ cat /etc/group | grep sudo
sudo:x:27:chris

log out & back in - sudo anything and you're still asked for a password

now
chris@HAL421:~$ sudo visduo
add NOPASSWD to the admin line at the bottom:
%admin ALL=(ALL) NOPASSWD: ALL
save, logout/login - sudo now no longer asks for a password