Consider the following pip requirements file:

numpy
Cython
astropy
aplpy

If one tries to install this using pip -r pip-requirements it will not work, because pip runs python setup.py egg_info on all packages first, but APLpy has a dependency on Astropy in setup.py. Is there a way we can avoid this issue, maybe by catching egg_info near the top of setup.py and simply running setup() for a limited set of options?