Can'nt remove group if non-ascii in name - schooltool-2.8.4

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Create group with cyrillic symbols in name.
Try to remove it.

schooltool-2.8.4
Ubuntu 15.10
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Exception

UnicodeEncodeError: 'ascii' codec can't encode characters in position 48-52: ordinal not in range(128)

Traceback

File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 132, in publish
  result = publication.callObject(request, obj)
File "/usr/lib/python2.7/dist-packages/zope/app/publication/zopepublication.py", line 205, in callObject
  return mapply(ob, request.getPositionalArguments(), request)
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 107, in mapply
  return debug_call(obj, args)
Extra information: schooltool.skin.flourish.zcml_content.FlourishGroupContainerDeleteView_delete.html object at 0x7f5243dac990
File "/usr/lib/python2.7/dist-packages/zope/publisher/publish.py", line 113, in debug_call
  return obj(*args)
File "/usr/lib/python2.7/dist-packages/schooltool/skin/flourish/page.py", line 98, in __call__
  self.update()
File "/usr/lib/python2.7/dist-packages/schooltool/skin/flourish/containers.py", line 46, in update
  self.request.response.redirect(self.nextURL())
File "/usr/lib/python2.7/dist-packages/zope/publisher/browser.py", line 759, in redirect
  return super(BrowserResponse, self).redirect(location, status, trusted)
File "/usr/lib/python2.7/dist-packages/zope/publisher/http.py", line 877, in redirect
  location = str(location)

Modules

schooltool 2.8.4 (/usr/lib/python2.7/dist-packages)
schooltool.cando 2.8.2 (/usr/lib/python2.7/dist-packages)
schooltool.gradebook 2.8.4.1 (/usr/lib/python2.7/dist-packages)
schooltool.intervention 2.7.1 (/usr/lib/python2.7/dist-packages)
schooltool.ldap 1.0.2 (/usr/lib/python2.7/dist-packages)
schooltool.lyceum.journal 2.8.2.1 (/usr/lib/python2.7/dist-packages)
schooltool.virginia 2.6.1 (/usr/lib/python2.7/dist-packages)

Runtime

Python 2.7.10 (default, Oct 14 2015, 16:09:02)
[GCC 5.2.1 20151010]
Linux ZAV 4.2.0-27-generic #32-Ubuntu SMP Fri Jan 22 04:49:08 UTC 2016 x86_64 x86_64
Filesystem encoding UTF-8, preferred UTF-8