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

I’m trying to create my first python package. To not bungle the whole deal, I’ve been attempting to upload it to the testpypi servers. That seems to go fine (sdist creates and upload doesn’t show any errors). However, when I try to install it to a new virtualenv from https://testpypi.python.org/pypi, it complains about my install requirements, e.g.:

How can I make setuptools install a package that’s not on PyPI?

I’ve just started working with setuptools and virtualenv. My package requires the latest python-gearman that is only available from GitHub. The python-gearman version that’s on PyPI is an old one. The Github source is setuptools-compatible, i.e. has setup.py, etc. Is there a way to make setuptools download and install the new version instead of looking for it on PyPI and installing the old one?