Mauricio Terrats

Not sure if this can help https://www.cyberciti.biz/faq/nginx-upstream-sent-too-big-header-while-reading-response-header-from-upstream/ . If you can provide more info it could help to understand how is it happening and how it can be fixed.

That means that cipi was not able to ssh to that server and download/execute the files it needs to create the site locally on the server. Are both servers running...

Why only gist and not your own pastebin? anyway +1 :)