buildout error : 'tuple' object has no attribute 'is_prerelease'

Hey guys,

I followed this doc :
http://mailman-bundler.readthedocs.org/en/latest/

and I get the following error at the buildout step

(venv)damien@gouda:~/dev/mailman-bundler$ buildout
While:
  Installing.
  Checking for upgrades.
  Getting distribution for 'distribute'.

An internal error occurred due to a bug in either zc.buildout or in a
recipe being used:
Traceback (most recent call last):
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/buildout.py", line 1946, in main
    getattr(buildout, command)(args)
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/buildout.py", line 475, in install
    self._maybe_upgrade()
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/buildout.py", line 910, in _maybe_upgrade
    allow_hosts = self._allow_hosts
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/easy_install.py", line 848, in install
    return installer.install(specs, working_set)
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/easy_install.py", line 635, in install
    for_buildout_run=for_buildout_run):
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/easy_install.py", line 477, in _get_dist
    dist, avail = self._satisfied(requirement)
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/easy_install.py", line 253, in _satisfied
    if _final_version(dist.parsed_version)
  File "/home/damien/dev/mailman-bundler/venv/local/lib/python2.7/site-packages/zc/buildout/easy_install.py", line 1408, in _final_version
    return not parsed_version.is_prerelease
AttributeError: 'tuple' object has no attribute 'is_prerelease'