Comment 21 for bug 1996909

I uploaded to my PPA docker.io not passing any mirror url to the debootstrap call in the basic-smoke test and fixed all the regressions:

Results: (from http://autopkgtest.ubuntu.com/results/autopkgtest-bionic-lucaskanashiro-container-backports/?format=plain)
  docker.io @ amd64:
    30.01.23 20:56:46 Log 🗒️ ✅ Triggers: docker.io/20.10.21-0ubuntu1~18.04.2~ppa2
  docker.io @ arm64:
    30.01.23 20:43:06 Log 🗒️ ⚪ Triggers: docker.io/20.10.21-0ubuntu1~18.04.2~ppa2
      No valid results
  docker.io @ armhf:
    30.01.23 20:29:56 Log 🗒️ ✅ Triggers: docker.io/20.10.21-0ubuntu1~18.04.2~ppa2
  docker.io @ ppc64el:
    30.01.23 20:43:27 Log 🗒️ ✅ Triggers: docker.io/20.10.21-0ubuntu1~18.04.2~ppa2
  docker.io @ s390x:

in arm64 there was an issue to set up the testbed but since it got fixed in the other architectures I expect the same for arm64. I'll be uploading a new version to -unapproved with this change.