UnicodeDecodeError in PloneFormGen after Plone Security patch 20161129

After applying the Plone security patch 20161129 our PloneFormGen form does not work anymore, because it contains Umlauts (ä, ö, ß or €). We use PloneFormGen 1.7.20 which is the recommended version for Plone 4.3.9. Here's the stacktrace:

  Module zope.tales.tales, line 696, in evaluate
   - URL: file:/var/plone/buildout-cache/eggs/Products.PloneFormGen-1.7.20-py2.7.egg/Products/PloneFormGen/skins/PloneFormGen/widget_fieldset_start.pt
   - Line 25, Column 10
   - Expression: <PythonExpr widget.Description(here)>
   - Names:
      {'container': <PloneSite at /mysite>,
       'context': <FormFolder at /mysite/mitglied-werden>,
       'desitelt': <object object at 0x7fe244f734b0>,
       'here': <FormFolder at /mysite/mitglied-werden>,
       'loop': {u'field': <Products.PageTemplates.Expressions.PathIterator object at 0x16fe5350>},
       'nothing': None,
       'options': {'args': (),
                   'state': <Products.CMFFormController.ControllerState.ControllerState object at 0x7fe22c676610>},
       'repeat': <Products.PageTemplates.Expressions.SafeMapping object at 0x1d61fc00>,
       'request': <HTTPRequest, URL=https://www.example.org/mitglied-werden/fg_base_view_p3>,
       'root': <Application at >,
       'template': <FSControllerPageTemplate at /mysite/fg_base_view_p3 used for /mysite/mitglied-werden>,
       'traverse_subpath': [],
       'user': <PloneUser 'siteb390'>}
  Module Products.PageTemplates.ZRPythonExpr, line 48, in __call__
   - __traceback_info__: widget.Description(here)
  Module PythonExpr, line 1, in <expression>
  Module Products.PloneFormGen.content.field_utils, line 27, in wDescription
  Module zope.i18n, line 107, in translate
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 20: ordinal not in range(128)

After removing the umlauts it works again, but the form looks a bit unprofessional now.

After searching the web for one hour now for just this error, I have no particular idea which extension causes this (PloneFormGen?) causes this and how to fix it :-/ Even no idea on which direction to look further...

Solution

Starting with 1.7.20, all PFG description fields are pushed through the translation mechanism. (Please don't ask me why they do that with user-supplied fields, because the description field is not language-insensitive in the first place.) Ths imposes additional limitations on what letters you can use in the description, as you have found.

Not claiming that this is a bugfix, but in my quick trial, modifying buildout-cache/eggs/Products.PloneFormGen-1.7.20-py2.7.egg/Products/PloneFormGen/content/field_utils.py line 27 from

        if value:
        value = translate(value, context=instance.REQUEST)
        return cgi.escape(value)

    if value:
        value = translate(value.decode('utf-8'), context=instance.REQUEST)
        return cgi.escape(value)

made the problem go away.