Generate nix expressions

Using pypi2nix with pip::

% pip install pypi2nix
% pypi2nix Plone --dists Plone --ignore Pillow --output plone.nix

or shorter:

% pypi2nix Plone -d Plone -i elementtree -o plone.nix

Using pypi2nix with zc.buildout::

[plone2nix]
recipe = pypi2nix
eggs = Plone
output = plone.nix
ignores =
    Pillow

Above section will generate plone2nix script which will call pypi2nix script with arguments defined in that section.

Using generated nix expresions in nixos

TODO