      }
  
      def __init__(self, queryset, cache_choices=False, required=True,
                   widget=None, label=None, initial=None,
                   help_text=None, *args, **kwargs):
          super(ModelMultipleChoiceField, self).__init__(queryset, None,
              cache_choices, required, widget, label, initial, help_text,
              *args, **kwargs)
  
      def clean(self, value):
 
</s> remove                  help_text=None, to_field_name=None, *args, **kwargs):
 </s> add                  help_text='', to_field_name=None, *args, **kwargs): </s> remove                  initial=None, help_text=None, *args, **kwargs):
 </s> add                  initial=None, help_text='', *args, **kwargs): </s> remove                  initial=None, help_text=None, *args, **kwargs):
 </s> add                  initial=None, help_text='', *args, **kwargs): </s> remove                  help_text=None, error_messages=None, show_hidden_initial=False,
 </s> add                  help_text='', error_messages=None, show_hidden_initial=False, </s> remove         if help_text is None:
            self.help_text = ''
        else:
            self.help_text = smart_text(help_text)
 </s> add         self.help_text = help_text
                 help_text='', *args, **kwargs):
      }
  
      def __init__(self, queryset, cache_choices=False, required=True,
                   widget=None, label=None, initial=None,
                 help_text='', *args, **kwargs):
          super(ModelMultipleChoiceField, self).__init__(queryset, None,
              cache_choices, required, widget, label, initial, help_text,
              *args, **kwargs)
  
      def clean(self, value):
keep keep keep keep replace keep keep keep keep keep
 Removed forced typecasting of help_text/label Field arguments

In any case, setting those variables to non-ascii utf-8 bytestrings
is now considered a programming error. 
django/forms/models.py