pythonPackages: remove name attribute`

The `buildPython*` function computes name from `pname` and `version`.
This change removes `name` attribute from all expressions in
`pkgs/development/python-modules`.

While at it, some other minor changes were made as well, such as
replacing `fetchurl` calls with `fetchPypi`.

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

@@ -1,11 +1,11 @@
-{ lib, buildPythonPackage, fetchurl, tornado }:
+{ lib, buildPythonPackage, fetchPypi, tornado }:
 
 buildPythonPackage rec {
-  name = "sockjs-tornado-${version}";
+  pname = "sockjs-tornado";
   version = "1.0.3";
 
-  src = fetchurl {
-    url = "mirror://pypi/s/sockjs-tornado/${name}.tar.gz";
+  src = fetchPypi {
+    inherit pname version;
     sha256 = "16cff40nniqsyvda1pb2j3b4zwmrw7y2g1vqq78lp20xpmhnwwkd";
   };