cookiecutter: 1.3.0 -> 1.4.0 (#19232)

This version bump changes the dependencies, adding in two new packages
`poyo` and `jinja2_time`.  This in turn fixes python3 support.

In order to get python3Packages.cookiecutter to build, I had to add pytest as
a dependency to whichcraft; I'm not sure why this wasn't already there.

I tried to build pypyPackages.cookiecutter, but the resulting binary
fails with the message:

    $ cookiecutter gh:audreyr/cookiecutter-pypackage
    Traceback (most recent call last):
      File "/nix/store/v1czxi8amljxkp6nxi8x1hxa7lkb6i7c-pypy5.4.1-cookiecutter-1.4.0/bin/.cookiecutter-wrapped", line 8, in <module>
        from cookiecutter.cli import main
    ImportError: No module named cookiecutter

I'm not sure how to debug this.