Apparently this doesn't work just yet. In debian/control I have X-Python3-Version: >= 3.5 This gives in the Depends: python3.5:any, python3:any (>= 3.5~) This cannot be statisfied because python3 the version in unstable is 3.4.3-7 -- Brian May <brian@linuxpenguins.xyz> https://linuxpenguins.xyz/brian/