I have to install bitcoin core to use op_return library. But I have difficulties to install correctly bitcoin core.
First I run the command sudo apt-add-repository ppa:bitcoin/bitcoin
Second I enter this command: apt-get update
But I have error :
Err http://ppa.launchpad.net jessie/main amd64 Packages
Err http://ppa.launchpad.net jessie/main amd64 Packages
Err http://ppa.launchpad.net jessie/main amd64 Packages
Err http://ppa.launchpad.net jessie/main amd64 Packages
Err http://ppa.launchpad.net jessie/main amd64 Packages
404 Not Found
W: Failed to fetch http:/ppa.launchpad.net/bitcoin/bitcoin/ubuntu/dists/jessie/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
So when I want to do this : apt-get install bitcoin-qt
I have : E: Unable to locate package bitcoin-qt
What can I do?