How can I ask setup.py to list dependencies?

You can get distutils to read setup.py and return you the dependencies. The command distutils.core.run_setup allows you to run setup.py in a controlled environment:

import distutils.core
setup = distutils.core.run_setup("setup.py")
print(setup.install_requires)

The Python variable setup has a set of properties which allow you to poke setup.py

python setup.py egg_info will write a package_name.egg-info/requires.txt file which contains the dependencies you want.