Package: pbuilder Version: 0.228.7 To reproduce the problem:
1. install apt-transport-tor apt update && apt install apt-transport-tor 2. configure sources.list to use apt-transport-tor cat > /etc/apt/sources.list << EOF deb tor+http://vwakviie2ienjx6t.onion/debian stretch main contrib non-free deb-src tor+http://vwakviie2ienjx6t.onion/debian stretch main contrib non-free deb tor+http://sgvtcaew4bxjd7ln.onion/debian-security stretch/updates main contrib non-free deb-src tor+http://sgvtcaew4bxjd7ln.onion/debian-security stretch/updates main contrib non-free # stretch-updates, previously known as 'volatile' deb tor+http://vwakviie2ienjx6t.onion/debian stretch-updates main contrib non-free deb-src tor+http://vwakviie2ienjx6t.onion/debian stretch-updates main contrib non-free # stretch-backports, previously on backports.debian.org deb tor+http://vwakviie2ienjx6t.onion/debian stretch-backports main contrib non-free deb-src tor+http://vwakviie2ienjx6t.onion/debian stretch-backports main contrib non-free EOF 3. try to install pbuilder apt update && apt install pbuilder 4. a dialog appears complaining that no valid sources were found, the user has to type another source URL such as the example URL http://httpredir.debian.org/debian