Where I should report these errors (nginx-custom)

I followed this guide, specially this part:

sudo add-apt-repository ppa:rtcamp/nginx
sudo apt-get update
sudo apt-get remove nginx*
sudo apt-get install nginx-custom

And now after sudo apt-get update I get this error:

W: The repository 'http://ppa.launchpad.net/rtcamp/nginx/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/rtcamp/nginx/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.

Main question: Where I should report it?

Subquestion: What does it say (mean)? :slight_smile:

I have the same problem using Ubuntu 16