Michal and I debugged this over IRC, and tracked it down. He had an /etc/apt/apt.conf with explicitly setting Architecture:, and creating an apt.Cache(rootdir="...") object still takes that global configuration into account.
The attached test as
Michal and I debugged this over IRC, and tracked it down. He had an /etc/apt/apt.conf with explicitly setting Architecture:, and creating an apt.Cache( rootdir= "...") object still takes that global configuration into account.
The attached test as