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/rocket-errbot/default.nix

@@ -1,11 +1,11 @@
-{ lib, fetchurl, fetchpatch, buildPythonPackage }:
+{ lib, fetchPypi, fetchpatch, buildPythonPackage }:
 
 buildPythonPackage rec {
-  name = "rocket-errbot-${version}";
+  pname = "rocket-errbot";
   version = "1.2.5";
 
-  src = fetchurl {
-    url = "mirror://pypi/r/rocket-errbot/${name}.tar.gz";
+  src = fetchPypi {
+    inherit pname version;
     sha256 = "181y1wqjvlry5xdzbliajvrxvswzh3myh795jnj1pm92r5grqzda";
   };