Bug#937811: python-hkdf: Python2 removal in sid/bullseye

[Sascha Steinbiss <satta@debian.org>]

It looks like all reverse deps are currently exclusively using the Python3 version: 

  [vagrant@debian:~/gnome-keysign] $ apt-rdepends -r python3-hkdf
  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  python3-hkdf
    Reverse Depends: magic-wormhole (0.11.2-1)
    Reverse Depends: python3-spake2 (0.8-2)
  magic-wormhole
    Reverse Depends: gnome-keysign (1.2.0-1)
  gnome-keysign
  python3-spake2
    Reverse Depends: magic-wormhole (>= 0.11.2-1)
  [vagrant@debian:~/gnome-keysign] $ apt-rdepends -r python-hkdf
  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  python-hkdf

I will prepare a QA upload removing the Python2 binary package then, if there are no objections.

Cheers
Sascha