[gentoo-alt] Bootstrapping fails

[John Yurcik]

I'm trying to follow the Gentoo Linux Documentation here: http://www.gentoo.org/proj/en/gentoo-alt/prefix/bootstrap.xml
When issuing the following command:

env FEATURES="-collision-protect" emerge --nodeps portage

prefix/bootstrap.xml The terminal outputs: Traceback (most recent call last):
  File "/Library/Gentoo/usr/bin/emerge", line 4471, in ?
    retval = emerge_main()
  File "/Library/Gentoo/usr/bin/emerge", line 4180, in emerge_main
    settings, trees, mtimedb = load_emerge_config()
  File "/Library/Gentoo/usr/bin/emerge", line 4091, in load_emerge_config
    trees = portage.create_trees(trees=trees, **kwargs)
  File "/Library/Gentoo/usr/lib/portage/pym/portage.py", line 7133, in create_trees
    config_incrementals=portage_const.INCREMENTALS)
  File "/Library/Gentoo/usr/lib/portage/pym/portage.py", line 1328, in __init__
    self.regenerate()
  File "/Library/Gentoo/usr/lib/portage/pym/portage.py", line 1733, in regenerate
    var_split.extend(expand_flags.difference(var_split))
  File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/sets.py", line 258, in difference
    return self - other
TypeError: unsupported operand type(s) for -: 'Set' and 'list'

I'm using a G4 powerbook running OS 10.3.9
Any ideas appreciated.