code: def mongoengine_validate_wrapper(old_clean, new_clean):
      
  
      def inner_validate(value):
          value = old_clean(value)
          try:
              new_clean(value)
              return value
          except ValidationError, e:
              raise forms.ValidationError(e)
      return inner_validate
docs: A wrapper function to validate formdata against mongoengine-field
      validator and raise a proper django.forms ValidationError if there
      are any problems.