Downgrading the buildd servers to sbuild-0.65.2 (24 Mar 2015) solved this issue. As you can see from the log below, the old sbuild version warns as well: -> sbuild: warning: can't parse dependency python3:native but it does not aborts the build.
Here is the log from sbuild-0.65.2: ------------------------------------ .... Fetched 4100 kB in 0s (4746 kB/s) Download complete and in download only mode Check architectures ─────────────────── sbuild: warning: can't parse dependency python3:native Check dependencies ────────────────── Merged Build-Depends: build-essential, fakeroot Filtered Build-Depends: build-essential, fakeroot dpkg-deb: building package 'sbuild-build-depends-core-dummy' in '/«BUILDDIR»/resolver-S87IhU/apt_archive/sbuild-build-depends-core-dummy.deb'. OK Ign file: ./ InRelease Get:1 file: ./ Release.gpg [299 B] Get:2 file: ./ Release [2119 B] Ign file: ./ Translation-en Reading package lists... Reading package lists... ┌──────────────────────────────────────────────────────────────────────────────┐ │ Install core build dependencies (apt-based resolver) │ └──────────────────────────────────────────────────────────────────────────────┘ ...