gpg: no valid OpenPGP data found in ubuntu

when I perform sudo add-apt-repository -y ppa:ethereum/ethereum this gives me an errors like,

gpg: keybox '/tmp/tmpy4v562r0/pubring.gpg' created gpg:

/tmp/tmpy4v562r0/trustdb.gpg: trustdb created gpg: key

1C52189C923F6CA9: public key "Launchpad PPA for Ethereum" imported

gpg: Total number processed: 1 gpg: imported: 1

**gpg: no valid OpenPGP data found.**

I tried many ways to solved but no luck.Please help me to solve this

Remove the Ethereum repository first:

sudo add-apt-repository --remove ppa:ethereum/ethereum
sudo apt update

Remove imported GPG key:

sudo apt-key del 2A518C819BE37D2C2031944D1C52189C923F6CA9

Import GPG key of the Ethereum repo again:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 2A518C819BE37D2C2031944D1C52189C923F6CA9

Add repository again:

sudo add-apt-repository -y ppa:ethereum/ethereum
sudo apt update

UPDATE

Remove the Ethereum repository again:

sudo add-apt-repository --remove ppa:ethereum/ethereum
sudo apt update

Remove imported GPG key:

sudo apt-key del 2A518C819BE37D2C2031944D1C52189C923F6CA9

Try

gpg --keyserver keyserver.ubuntu.com --recv-keys 2a518c819be37d2c2031944d1c52189c923f6ca9

and next

gpg --export --armor 2a518c819be37d2c2031944d1c52189c923f6ca9 | sudo apt-key add -

Add repository for Ubuntu 16.04:

echo -e "deb http://ppa.launchpad.net/ethereum/ethereum/ubuntu xenial main" | sudo tee /etc/apt/sources.list.d/ethereum-ubuntu-ethereum-xenial.list

Update apt:

sudo apt update

Install software you want from the Ethereum repository.