pip requirements.txt with alternative index

I want to put all the requirements of a repoze Zope2 install in a pip requirements file. Most of the repoze packages don't seem to be on PyPi, but there's an alternative PyPi index for them here. But I can't figure out how to tell pip to use that index together with a requirements file. For single packages, it's easy ``` pip install zopelib -i http://dist.repoze.org/zope2/2.10/simple/ ``` I tried the following ``` pip install -r requirements.txt -i http://dist.repoze.org/zope2/2.10/simple/ ``` or in my requirements.txt all kind or permutations of these: ``` zopelib -i http://dist.repoze.org/zope2/2.10/simple/ zopelib --index http://dist.repoze.org/zope2/2.10/simple/ -i http://dist.repoze.org/zope2/2.10/simple/ zopelib ``` or (because the documentation says "Note that all these options must be on a line of their own.") ``` --index http://dist.repoze.org/zope2/2.10/simple/ zopelib ``` So, what's the correct way of telling pip to use http://dist.repoze.org/zope2/2.10/simple/ as index?