activator: remove package from package-set

the typesafe activator is about to reach end of life at the end of this
month (2017-05) and the servers will be decommissioned at the ond of 2017.

See http://www.lightbend.com/community/core-tools/activator-and-sbt for
and the project's readme
(https://github.com/typesafehub/activator/blob/master/README.md) for further reference.

pkgs/development/tools/activator/default.nix

@@ -1,32 +0,0 @@
-{ stdenv, fetchurl, unzip, jre }:
-
-stdenv.mkDerivation rec {
-
-  name = "${pname}-${version}";
-  pname = "activator";
-  version = "1.3.12";
-
-  src = fetchurl {
-    url = "http://downloads.typesafe.com/typesafe-${pname}/${version}/typesafe-${name}.zip";
-    sha256 = "0c7mxznfgvywnyvr8l5jh4cp67ila5cdq14p6jwrkh6lwif3ah1p";
-  };
-
-  buildInputs = [ unzip jre ];
-
-  installPhase = ''
-    mkdir -p $out/{bin,lib,libexec}
-    mv repository $out/lib
-    sed -i -e "s,declare.*activator_home.*=.*,declare -r activator_home=$out/lib/,g" bin/activator
-    mv bin/activator $out/bin
-    mv libexec/activator-launch-${version}.jar $out/libexec
-  '';
-
-  meta = with stdenv.lib; {
-    description = "A scafollding tool for setting up reactive projects";
-    homepage = "http://typesafe.com/activator";
-    license = licenses.asl20;
-    maintainers = with maintainers; [ edwtjo cko ];
-    platforms = with platforms; unix;
-  };
-
-}

pkgs/top-level/all-packages.nix

@@ -6320,7 +6320,13 @@ with pkgs;
 
   ### DEVELOPMENT / TOOLS
 
-  activator = callPackage ../development/tools/activator { };
+  activator = throw ''
+    Typesafe Activator was removed in 2017-05-08 as the actual package reaches end of life.
+
+    See https://github.com/NixOS/nixpkgs/pull/25616
+    and http://www.lightbend.com/community/core-tools/activator-and-sbt
+    for more information.
+  '';
 
   alloy = callPackage ../development/tools/alloy { };