Pip install from pypi works, but from testpypi fails (cannot find requirements)

Update

PyPI has upgraded its site. According to the docs, the new advice is:

python -m pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple poirot

• --index-url points to your package on TestPyPI.
• --extra-index-url points to dependencies on PyPI.
• poirot is your package.

Caution: despite this recommendation from the official docs, using --extra-index-url can be unsafe in certain situations, particularly on private servers. See also A. Sottile’s video demonstrating the risks related to option ordering and mixing public with private PyPI servers. Use with caution and assess your own risks.

Out-dated

Try pip install --extra-index-url https://testpypi.python.org/pypi poirot.

See also a reference post.