Schooltool crashes if ldap user has non-ascii characters in their names

I'm trying to implement SchoolTool with zentyal for my kids school.
This is testing environment at the moment because I can't show school staff the demo.

Problem is that teachers have scandic letters in their names (not the user id).

Trace:
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 129, in publish
  obj = request.traverse(obj)
File "/usr/lib/python2.7/dist-packages/zope/publisher/browser.py", line 540, in traverse
  ob = super(BrowserRequest, self).traverse(obj)
File "/usr/lib/python2.7/dist-packages/zope/publisher/http.py", line 457, in traverse
  ob = super(HTTPRequest, self).traverse(obj)
File "/usr/lib/python2.7/dist-packages/zope/publisher/base.py", line 249, in traverse
  publication.callTraversalHooks(self, obj)
File "/usr/lib/python2.7/dist-packages/zope/app/publication/zopepublication.py", line 137, in callTraversalHooks
  self._maybePlacefullyAuthenticate(request, ob)
File "/usr/lib/python2.7/dist-packages/zope/app/publication/zopepublication.py", line 124, in _maybePlacefullyAuthenticate
  principal = auth.authenticate(request)
File "/usr/lib/python2.7/dist-packages/schooltool/app/security.py", line 220, in authenticate
  return self.authPlugin.authenticate(request)
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 304, in authenticate
  principal = self.getPrincipal('sb.person.' + session['username'])
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 370, in getPrincipal
  ldap_person.update()
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 476, in update
  super(LDAPPerson, self).update()
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 462, in update
  part.update()
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 639, in update
  super(PersonLDAPInetOrgPersonPart, self).update()
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 600, in update
  super(PersonLDAPOrganizationalPersonPart, self).update()
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 574, in update
  'first_name': self.oneline(self.data.cn),
File "/usr/lib/python2.7/dist-packages/schooltool/ldap/security.py", line 569, in oneline
  return t and (u' '.join(t)).strip() or u''

Name in zentyal ldap is "Nina Mäkelä"

I can change that name to Makela, but then every other aplication shows that too.

- Samuli