How can I install packages hosted in a private PyPI using setup.py?

it looks like you didnt specify your host like the doc of simplepy said you need to setup your ~/.pypirc with the good hostname like

To use it run "simplepypi". You can upload packages by:

[...]

Not using twine yet? Here is the legacy way of uploading Python packages (not recommended):

Modify your ~/.pypirc so it looks like:

[distutils]
index-servers =
    pypi
    local

[local]
username: <whatever>
password: <doesn't matter, see above>
repository: http://127.0.0.1:8000

[pypi]
...

then you'll upload your package on it

python setup.py sdist upload -r local

and could install it from there

pip install -i http://127.0.0.1:8000/pypi <your favorite package>

Hope this will help.