Q: Why did I receive an error about signature verification when trying to update my Debathena machine?

Answer

While updating you may see an error similar to this one:

W: A error occurred during the signature verification. The repository
is not updated and the previous index files will be used.GPG error:
http://debathena.mit.edu hardy Release: The following signatures
couldn't be verified because the public key is not available: NO_PUBKEY 
E4EE62700D8A9E8F

Please make sure you have the latest Debathena archive key. You can do that with the following procedure:

1. cd $HOME
2. wget -N http://debathena.mit.edu/apt/debathena-archive.asc
3. sudo apt-key add debathena-archive.asc
   You will be prompted to enter your administrative password for your machine.