option to run a requirements.txt install first
it's reasonable to want to maintain both install_requires and a requirements.txt. http://stackoverflow.com/a/7085000
if you're doing that, there seems to be no way to lay down the requirements first before your distribution gets installed, which is what you want.
I see a number of people adding "pip install -r requirements.txt" lines into the the test command option, but that's happening after the distribution is installed.