When using the GPGKEY option, aptitude don't trust the repository and apt-get simply ignore the repo. Sounds that because the master Release doesn't contain the md5 for uncompressed "Packages" file. ===================================================================
Drop Contents.head since it has no useful purpose. https://bugs.debian.org/676642 https://bugs.debian.org/841997 https://bugs.launchpad.net/bugs/1638219