Comment 3 for bug 1682820

I can't install synaptic, or anything else, because 'apt' fails to run, with:

$ apt-cache policy python3-minimal
python3-minimal:
  Installed: 3.5.3-1
  Candidate: 3.5.3-1
  Version table:
 *** 3.5.3-1 500
        500 http://gb.archive.ubuntu.com/ubuntu zesty/main amd64 Packages
        100 /var/lib/dpkg/status

Is there another way I can do the cleaning?