Throws UnicodeDecodeError on page/folder view with scaled image

[jnachtigall]

After installation with buildout (regardless of being installed via quick installer or not), it throws an error on every page that contains an image:

Traceback (innermost last):
  Module ZPublisher.Publish, line 138, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module Shared.DC.Scripts.Bindings, line 322, in __call__
  Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec
  Module Products.PageTemplates.ZopePageTemplate, line 338, in _exec
  Module Products.PageTemplates.ZopePageTemplate, line 435, in pt_render
  Module Products.PageTemplates.PageTemplate, line 79, in pt_render
  Module zope.pagetemplate.pagetemplate, line 132, in pt_render
   - Warning: Macro expansion failed
   - Warning: <type 'exceptions.KeyError'>: 'imageCaption'
  Module zope.pagetemplate.pagetemplate, line 240, in __call__
  Module zope.tal.talinterpreter, line 271, in __call__
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 888, in do_useMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 954, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 858, in do_defineMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 954, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 954, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 946, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 858, in do_defineMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 888, in do_useMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 858, in do_defineMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 852, in do_condition
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 946, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 888, in do_useMacro
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 821, in do_loop_tal
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 946, in do_defineSlot
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 533, in do_optTag_tal
  Module zope.tal.talinterpreter, line 518, in do_optTag
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 852, in do_condition
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 531, in do_optTag_tal
  Module zope.tal.talinterpreter, line 513, in no_tag
  Module zope.tal.talinterpreter, line 343, in interpret
  Module zope.tal.talinterpreter, line 742, in do_insertStructure_tal
  Module Products.PageTemplates.Expressions, line 218, in evaluateStructure
  Module zope.tales.tales, line 696, in evaluate
   - URL: /mysite/folder_strukturen_summary_view
   - Line 160, Column 24
   - Expression: <PythonExpr path('nocall:item_object/tag')(scale='leadimage', css_class='tileImage')>
   - Names:
      {'container': <PloneSite at /mysite>,
       'context': <ATTopic at /mysite/folder-with-image>,
       'default': <object object at 0x801d6d4e0>,
       'here': <ATTopic at /mysite/folder-with-image>,
       'loop': {u'item': <Products.PageTemplates.Expressions.PathIterator object at 0x81c0225d0>},
       'nothing': None,
       'options': {'args': ()},
       'repeat': <Products.PageTemplates.Expressions.SafeMapping object at 0x819ae9d60>,
       'request': <HTTPRequest, URL=https://mysite.org/folder-with-image/folder_strukturen_summary_view>,
       'root': <Application at >,
       'template': <ZopePageTemplate at /mysite/folder_strukturen_summary_view used for /mysite/folder-with-image>,
       'traverse_subpath': [],
       'user': <PloneUser 'admin-user'>}
  Module Products.PageTemplates.ZRPythonExpr, line 48, in __call__
   - __traceback_info__: path('nocall:item_object/tag')(scale='leadimage', css_class='tileImage')
  Module PythonExpr, line 1, in <expression>
  Module Products.ATContentTypes.content.newsitem, line 113, in tag
  Module raptus.multilanguagefields.fields, line 397, in tag
  Module Products.Archetypes.Field, line 2729, in tag
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 21: ordinal not in range(128)