Motivation for this change

https://lists.gnupg.org/pipermail/gnupg-announce/2017q3/000411.html

Noteworthy changes in version 2.1.22

• gpg: Extend command --quick-set-expire to allow for setting the
  expiration time of subkeys.
• gpg: By default try to repair keys during import. New sub-option
  no-repair-keys for --import-options.
• gpg,gpgsm: Improved checking and reporting of DE-VS compliance.
• gpg: New options --key-origin and --with-key-origin. Store the
  time of the last key update from keyservers, WKD, or DANE.
• agent: New option --ssh-fingerprint-digest.
• dimngr: Lower timeouts on keyserver connection attempts and made
  it configurable.
• dirmngr: Tor will now automatically be detected and used. The
  option --no-use-tor disables Tor detection.
• dirmngr: Now detects a changed /etc/resolv.conf.
• agent,dirmngr: Initiate shutdown on removal of the GnuPG home
  directory.
• gpg: Avoid caching passphrase for failed symmetric encryption.
• agent: Support for unprotected ssh keys.
• dirmngr: Fixed name resolving on systems using only v6
  nameservers.
• dirmngr: Allow the use of TLS over http proxies.
• w32: Change directory of the daemons after startup.
• wks: New man pages for client and server.

Things done

Please check what applies. Note that these are not hard requirements but merely serve as information for reviewers.

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.