Unfortunately, his instructions are slightly out of date - the key has changed again.
To fix this issue:
1. Import the apt repository key with this command:
Code:
gpg --keyserver keyring.debian.org --recv 010908312D230C5F
2. Export the key into the local apt keyring:
Code:
gpg --armor --export 2D230C5F | apt-key add -
3. Run apt-get update to make your local listings coherent.
Once I did that I was once again able to update.