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/mnemonic/default.nix

@@ -1,12 +1,11 @@
-{ lib, fetchurl, buildPythonPackage, pbkdf2 }:
+{ lib, fetchPypi, buildPythonPackage, pbkdf2 }:
 
 buildPythonPackage rec {
   pname = "mnemonic";
   version = "0.18";
-  name = "${pname}-${version}";
 
-  src = fetchurl {
-    url = "mirror://pypi/m/${pname}/${name}.tar.gz";
+  src = fetchPypi {
+    inherit pname version;
     sha256 = "02a7306a792370f4a0c106c2cf1ce5a0c84b9dbd7e71c6792fdb9ad88a727f1d";
   };