How to fix the Ubuntu GPG Error BADSIG

If you are seeing Ubuntu GPG Error BADSIG use the one of the following methods to fix
Error Message
W: GPG error: http://archive.canonical.com intrepid Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key 

Try to run the following comamnds from terminal

$ sudo -i
# apt-get clean
# cd /var/lib/apt
# mv lists lists.old
# mkdir -p lists/partial
# apt-get clean
# apt-get update