[Distutils] (How) do setuptools/distribute handle circular dependencies?

[Vinay Sajip]

Working on distlib, I noticed that PyPI contains projects with circular
dependencies. Here's an extract from setup.py in the latest Zope2 (2.13.19):

    install_requires=[
      ...
      'Products.OFSP >= 2.13.2',
      ...
    ] + additional_install_requires,

whereas the the setup.py in the latest Products.OFSP (2.13.2) has:

      install_requires=[
        ...
        'Zope2 >= 2.13.0a1',
      ],

So, according to the declarations, each package depends on the other. Can
setuptools / distribute deal with this sort of situation? If so, how does
that work?

Regards,

Vinay Sajip