ENV=pure-private fails on Travis

[dHannasch]

running check
warning: Check: missing required meta-data: url
error: Please correct your package.
ERROR: InvocationError for command /home/travis/build/ionelmc/cookiecutter-pylibrary/python-nameless/.tox/check/bin/python setup.py check --strict --metadata --restructuredtext (exited with code 1)

https://docs.python.org/3/distutils/examples.html#checking-a-package

distutils is complaining because no url argument is provided. This is intended behavior in setup.py,

{%- if cookiecutter.repo_hosting_domain != "no" %}
    url='https://{{ cookiecutter.repo_hosting_domain }}/{{ cookiecutter.repo_username }}/{{ cookiecutter.repo_name }}',
{%- endif %}

but distutils obviously doesn't like it. I don't immediately see a way to tell distutils to let the URL thing slide without eliminating the check altogether.