The general case is that buildout will pick versions for setuptools,
pip and wheel when they are not pinned: it's only when these are
installed as .egg-link - either as actual develop eggs or as a
side-effect of being found in .dist-info format in the environment
e.g. in site-packages - that buildout does not consider it picked
a version for these eggs.

This affects tests that set `allow-picked-versions = false` or
`show-picked-versions = true` or `update-versions-file = ...`.