user38652: I want to use python-OP_RETURN library. 
For this I need to install bitcoin core. 
But when I exceute this command
sudo apt-get update I have this 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
Get:2 http://security.debian.org jessie/updates/main amd64 Packages [371 kB]                                         
Ign http://httpredir.debian.org jessie InRelease                                                                         
Get:3 http://httpredir.debian.org jessie-updates InRelease [142 kB]                       
Hit http://httpredir.debian.org jessie Release.gpg
Hit http://httpredir.debian.org jessie Release              
Get:4 http://httpredir.debian.org jessie-updates/main amd64 Packages [17.6 kB]
Get:5 http://httpredir.debian.org jessie/main amd64 Packages [9032 kB]
Fetched 9626 kB in 8s (1085 kB/s)                                                                                                                                                                                                          
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.

What does it mean? 

user33314: Your on debian the bitcoin PPA only works on ubuntu.
See this guide to build it on debian.
https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md

38652: <p>I want to use python-OP_RETURN library. 
For this I need to install bitcoin core. 
But when I exceute this command
<code>sudo apt-get update</code> I have this error : </p>

<pre><code>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
Get:2 http://security.debian.org jessie/updates/main amd64 Packages [371 kB]                                         
Ign http://httpredir.debian.org jessie InRelease                                                                         
Get:3 http://httpredir.debian.org jessie-updates InRelease [142 kB]                       
Hit http://httpredir.debian.org jessie Release.gpg
Hit http://httpredir.debian.org jessie Release              
Get:4 http://httpredir.debian.org jessie-updates/main amd64 Packages [17.6 kB]
Get:5 http://httpredir.debian.org jessie/main amd64 Packages [9032 kB]
Fetched 9626 kB in 8s (1085 kB/s)                                                                                                                                                                                                          
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.
</code></pre>

<p>What does it mean? </p>
 33314: <p>Your on debian the bitcoin PPA only works on ubuntu.
See this guide to build it on debian.
<a href="https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md" rel="nofollow">https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md</a></p>
