Solving Package 'xyz' has no installation candidate !!

During installing any package in ubuntu, if we encounter "no installation candidate" error, we first have to run the following two commands.

sudo apt-get clean
sudo apt-get update

Then you can try re installing the package.

However there are at times when we come across an error "A error occured during the signature verification". In such cases the installation of the package cannot be proceeded.

I followed this link and could solve the problem. Following are the list of commands mentioned in the link to solve the problem.
           

sudo apt-get clean
sudo mv /var/lib/apt/lists /tmp
sudo mkdir -p /var/lib/apt/lists/partial
sudo apt-get clean
sudo apt-get update

After running the above commands, the signature verification error will be gone. we can resume the installation of the original package.

Passionately,
Achutha