[#1459 ZMI folder manage_main breaks in _encode_unicode]

Another report from saper, like #1450 but in a different place.  I have reproduced it with zope 2.11, viewing manage_main on a wiki folder containing pages with non-ascii names::

 Traceback (innermost last):
  Module ZPublisher.Publish, line 122, in publish
  Module ZServer.HTTPResponse, line 262, in setBody
  Module ZPublisher.HTTPResponse, line 324, in setBody
  Module ZPublisher.HTTPResponse, line 476, in _encode_unicode
 UnicodeEncodeError: 'latin-1' codec can't encode characters in position 16387-16389: ordinal not in range(256)


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forwarded from http://zwiki.org/1459ZMIFolderManageMainBreaksInEncodeUnicode#[email protected]