gns3-server: improve expression

pkgs/applications/networking/gns3/server.nix

@@ -1,63 +1,54 @@
 { stable, branch, version, sha256Hash }:
 
-{ stdenv, python36Packages, fetchFromGitHub, fetchurl }:
+{ stdenv, python36, fetchFromGitHub }:
 
 let
-  pythonPackages = python36Packages;
-  async-timeout = pythonPackages.async-timeout.overrideAttrs
-    (oldAttrs:
-      rec {
-        pname = "async-timeout";
+  python = python36.override {
+    packageOverrides = self: super: {
+      async-timeout = super.async-timeout.overridePythonAttrs (oldAttrs: rec {
         version = "2.0.1";
-        src = pythonPackages.fetchPypi {
-          inherit pname version;
+        src = oldAttrs.src.override {
+          inherit version;
           sha256 = "1l3kg062m02mph6rf9rdv8r5c5n356clxa6b6mrn0i77vk9g9kq0";
         };
       });
-  aiohttp = pythonPackages.aiohttp.overrideAttrs
-    (oldAttrs:
-      rec {
-        pname = "aiohttp";
+      aiohttp = super.aiohttp.overridePythonAttrs (oldAttrs: rec {
         version = "2.3.10";
-        src = pythonPackages.fetchPypi {
-          inherit pname version;
+        src = oldAttrs.src.override {
+          inherit version;
           sha256 = "8adda6583ba438a4c70693374e10b60168663ffa6564c5c75d3c7a9055290964";
         };
-        propagatedBuildInputs = [ async-timeout ]
-          ++ (with pythonPackages; [ attrs chardet multidict yarl idna-ssl ]);
+        propagatedBuildInputs = with self; [ async-timeout attrs chardet multidict yarl idna-ssl ];
+        doCheck = false;
       });
-  aiohttp-cors = pythonPackages.aiohttp-cors.overrideAttrs
-    (oldAttrs:
-      rec {
-        pname = "aiohttp-cors";
+      aiohttp-cors = super.aiohttp-cors.overridePythonAttrs (oldAttrs: rec {
         version = "0.5.3";
-        name = "${pname}-${version}";
-        src = pythonPackages.fetchPypi {
-          inherit pname version;
+        src = oldAttrs.src.override {
+          inherit version;
           sha256 = "11b51mhr7wjfiikvj3nc5s8c7miin2zdhl3yrzcga4mbpkj892in";
         };
-        propagatedBuildInputs = [ aiohttp ]
-          ++ stdenv.lib.optional
-               (pythonPackages.pythonOlder "3.5")
-               pythonPackages.typing;
+        propagatedBuildInputs = with self; [ aiohttp ]
+          ++ stdenv.lib.optional (pythonOlder "3.5") typing;
       });
-in pythonPackages.buildPythonPackage rec {
-  name = "${pname}-${version}";
+    };
+  };
+
+in python.pkgs.buildPythonPackage {
   pname = "gns3-server";
+  inherit version;
 
   src = fetchFromGitHub {
     owner = "GNS3";
-    repo = pname;
+    repo = "gns3-server";
     rev = "v${version}";
     sha256 = sha256Hash;
   };
 
-  propagatedBuildInputs = [ aiohttp-cors ]
-    ++ (with pythonPackages; [
-      yarl aiohttp multidict
-      jinja2 psutil zipstream raven jsonschema typing
-      (pythonPackages.callPackage ../../../development/python-modules/prompt_toolkit/1.nix {})
-    ]);
+  propagatedBuildInputs = with python.pkgs; [
+    aiohttp-cors yarl aiohttp multidict
+    jinja2 psutil zipstream raven jsonschema typing
+    (python.pkgs.callPackage ../../../development/python-modules/prompt_toolkit/1.nix {})
+  ];
 
   # Requires network access
   doCheck = false;
@@ -65,6 +56,7 @@ in pythonPackages.buildPythonPackage rec {
   postInstall = ''
     rm $out/bin/gns3loopback # For Windows only
   '';
+
   meta = with stdenv.lib; {
     description = "Graphical Network Simulator 3 server (${branch} release)";
     longDescription = ''