[Distutils] Declaring "already provided" modules

[Martin Aspeli]

Hi guys,

I have a particular problem which I think we'll see a lot more of going 
forward. Zope 3 is in the process of being eggified, and we have eggs in 
the cheesehop of things like zope.component 3.4.0a1.

I use zc.buildout to configure a Zope instance (a zope 2.10 one, to be 
precise) which has the various zope.* packages in non-egg-format in 
$INSTANCE_HOME/lib/python/zope/*.

Then I'm depending on a package which does this:

       install_requires=['setuptools',
                         ''zope.component',
                          'zope.interface',
                          'zope.schema',
                        ],

The problem is that even though I know I have zope.component 3.3 from my 
Zope instance, setuptools/buildout doesn't know that and tries to 
resolve the dependency. It succeeds with Zope 3.4's zope.component, 
which then causes runtime conflicts and subtle problems all over the place.

I think what I need is some way of saying "all of these dependencies are 
already resolved, don't try to get them as new eggs". Is that possible? 
Is there another way I can manage this?

Martin