Manually remove trailing white spaces
in `pkgs/**.nix` with the help of an editor
Auto-generated nix expressions containing trailing whitespaces:
* pkgs/development/haskell-modules/hackage-packages.nix
* See issue https://github.com/NixOS/cabal2nix/issues/208
* pkgs/**/eggs.nix
* I don't know how they are generated,
but they seems to be Python-related.