salt: fix darwin build by specifying dependency on tornado 4

/cc ZHF #45961

pkgs/development/python-modules/tornado/default.nix

@@ -8,12 +8,25 @@
 , singledispatch
 , pythonOlder
 , futures
+, version ? "5.1"
 }:
 
+let
+  versionMap = {
+    "4.5.3" = {
+      sha256 = "02jzd23l4r6fswmwxaica9ldlyc2p6q8dk6dyff7j58fmdzf853d";
+    };
+    "5.1" = {
+      sha256 = "4f66a2172cb947387193ca4c2c3e19131f1c70fa8be470ddbbd9317fd0801582";
+    };
+  };
+in
+
+with versionMap.${version};
+
 buildPythonPackage rec {
   pname = "tornado";
-  version = "5.1";
-
+  inherit version;
 
   propagatedBuildInputs = [ backports_abc  certifi singledispatch ]
     ++ lib.optional (pythonOlder "3.5") backports_ssl_match_hostname
@@ -26,8 +39,7 @@ buildPythonPackage rec {
   '';
 
   src = fetchPypi {
-    inherit pname version;
-    sha256 = "4f66a2172cb947387193ca4c2c3e19131f1c70fa8be470ddbbd9317fd0801582";
+    inherit pname sha256 version;
   };
 
   meta = {

pkgs/tools/admin/salt/default.nix

@@ -23,7 +23,7 @@ pythonPackages.buildPythonApplication rec {
     pyyaml
     pyzmq
     requests
-    tornado
+    tornado_4
   ] ++ stdenv.lib.optional (!pythonPackages.isPy3k) [
     futures
   ] ++ extraInputs;

pkgs/top-level/python-packages.nix

@@ -14901,6 +14901,7 @@ EOF
   };
 
   tornado = callPackage ../development/python-modules/tornado { };
+  tornado_4 = callPackage ../development/python-modules/tornado { version = "4.5.3"; };
 
   tokenlib = buildPythonPackage rec {
     name = "tokenlib-${version}";