tests/hetzner/repos: Pin GnuPG version to v2.0

I ran into this while trying to run tests prior to merging #564 (merge
commit b09e618).

The default GnuPG version in <nixpkgs> is 2.1, but the Debian version
used while building the Debian repository is GnuPG version 2.0, so we
need to make sure both versions match at least in major and minor.

The test for the Hetzner backend now still fails, but at least it
doesn't fail anymore because one of its dependencies are failing.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

tests/hetzner-backend/repository.nix

@@ -3,6 +3,9 @@
 }:
 
 let
+  # Has to match with the version used in the Debian repository.
+  gnupg = pkgs.gnupg20;
+
   reprepro = pkgs.stdenv.mkDerivation rec {
     name = "reprepro-${version}";
     version = "4.16.0";
@@ -13,10 +16,12 @@ let
       sha256 = "14gmk16k9n04xda4446ydfj8cr5pmzsmm4il8ysf69ivybiwmlpx";
     };
 
-    buildInputs = with pkgs; [ makeWrapper db gpgme libarchive bzip2 xz zlib ];
+    nativeBuildInputs = [ pkgs.makeWrapper ];
+    buildInputs = pkgs.lib.singleton (pkgs.gpgme.override { inherit gnupg; })
+               ++ (with pkgs; [ db libarchive bzip2 xz zlib ]);
 
     postInstall = ''
-      wrapProgram "$out/bin/reprepro" --prefix PATH : "${pkgs.gnupg}/bin"
+      wrapProgram "$out/bin/reprepro" --prefix PATH : "${gnupg}/bin"
     '';
   };
 
@@ -45,13 +50,13 @@ let
       %echo Repository key created
       EOF
 
-      ${pkgs.gnupg}/bin/gpg2 --batch --gen-key template
+      ${gnupg}/bin/gpg2 --batch --gen-key template
 
-      ${pkgs.gnupg}/bin/gpg2 --list-secret-keys --with-colons | \
+      ${gnupg}/bin/gpg2 --list-secret-keys --with-colons | \
         grep '^sec:' | cut -d: -f5 > "$secretKeyId"
-      ${pkgs.gnupg}/bin/gpg2 --list-public-keys --with-colons | \
+      ${gnupg}/bin/gpg2 --list-public-keys --with-colons | \
         grep '^pub:' | cut -d: -f5 > "$publicKeyId"
-      ${pkgs.gnupg}/bin/gpg2 --export \
+      ${gnupg}/bin/gpg2 --export \
         "$(< "$publicKeyId")" \
         > "$publicKey"
     '';