Fixes the Hydra CI build of `python{3,2}Packages.keyutils` on `nixpkgs.`
This patch changes the source retrieval to fetchFromGitHub as the PYPI
tarball doesn't come with tests for the check phase.
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`.
