​I can reproduce the problems.

I do not understand at all, why buildout does not add persistent into the path for zope.traverser. Through dependency chains it depends on BTrees and BTrees depends on persistent, still, persistent is not in the paths for my script. Marius, can you show me your buildout script and your test script for zope traverser? Mine is:

do3cc@BRICK> cat bin/buildout  | sed -e 's/\( *\).*\(\/[^\/]*\)\(\/[^\/]*\)/\1\2\3/'
/bin/python

import sys
sys.path[0:0] = [
  /eggs/distribute-0.6.35-py2.7.egg',
  /eggs/zc.buildout-2.0.1-py2.7.egg',
  ]

import zc.buildout.buildout

if __name__ == '__main__':
    sys.exit(zc.buildout.buildout.main())
do3cc@BRICK> cat bin/test-ztk-zope.traversing  | sed -e 's/\( *\).*\(\/[^\/]*\)\(\/[^\/]*\)/\1\2\3/'
/bin/python

import sys
sys.path[0:0] = [
  /zope.traversing/src',
  /zope.testrunner/src',
  /zope.interface/src',
  /zope.exceptions/src',
  /eggs/six-1.2.0-py2.7.egg',
  /eggs/distribute-0.6.35-py2.7.egg',
  /zope.testing/src',
  /zope.tales/src',
  /zope.security/src',
  /zope.configuration/src',
  /zope.component/src',
  /zope.browserresource/src',
  /zope.annotation/src',
  /zope.publisher/src',
  /zope.proxy/src',
  /zope.location/src',
  /zope.i18nmessageid/src',
  /zope.i18n/src',
  /src/transaction',
  /src/BTrees',
  /zope.schema/src',
  /zope.event/src',
  /zope.contenttype/src',
  /zope.browser/src',
  /eggs/pytz-2012j-py2.7.egg',
  ]

import os
sys.argv[0] = os.path.abspath(sys.argv[0])
/parts/test-ztk-zope.traversing')


import zope.testrunner

if __name__ == '__main__':
    sys.exit(zope.testrunner.run([
        /zope.traversing/src',
        ]))

I am using python 2.7