setuptools.setup offers its install_requires argument. Specified packages are installed at the end of setup.py. It seems like there're other requirements sections as well (tests_require and requirements). I didn't find any info on the latter because help(setuptools.setup) doesn't contain any useful information about it's arguments. I checked the source of distutils.Distribution distutils/dist.py, but it doesn't contain useful documentation (one might say - at all).
I know that setuptools isn't self-bootstrapping (like e.g. maven). It just want to make sure I'm not missing something.
I can imagine straightforward workarounds like installating with pip and subprocress.* functions. I'm looking for a declarative solution.
Maybe what you need is the setup_requires parameter: Building and Distributing Packages with Setuptools