$ python2.4 bootstrap.py -c demo-plone3.fg $ bin/buildout -c demo-plone3.cfg
$ python2.6 bootstrap.py -c demo.cfg $ bin/buildout -c demo.cfg
or, if you prefer to use virtualenv (apt-get install python-virtualenv):
$ virtualenv --python=/usr/bin/python2.6 . $ bin/python2.6 bootstrap.py -c demo.cfg $ bin/buildout -c demo.cfg
More info at http://www.plone4bio.org