https://bugs.launchpad.net/zc.buildout/+bug/239212 is indeed solved
  in trunk

- fixed the test for the += -= syntax change.

  attribute '_logger'""" by providing reasonable defaults 
  within the Buildout constructor (related to the new 'allow-hosts' option)
  (patch by Gottfried Ganssauge) (ajung)

- Quote the 'spec' argument, as in the case of installing an egg from
  the buildout-cache, if the filename contains spaces it would fail

AttributeError:
Buildout instance has no attribute '_logger' 

- 1.0.2 release

This change reduces test failures on my current platform from 48 to 3.
I hope it doesn't break zc.buildout on any other platform.

- further rmtree fixes for Windows

  Gottfried Ganssauge) (ajung)

- allowed to interpolate variables with the environment

- make sure the environment is cleaned

Remove gibberish paragraph from variable substitution section (was this ever true?), correct next paragraph to reflect current example.