docs: def _decode_unicode(value, charset, errors):
      """Like the regular decode function but this one raises an
      `HTTPUnicodeError` if errors is `strict`."""
      fallback = None
      if errors.startswith('fallback:'):
          fallback = errors[9:]
          errors = 'strict'
      try:
          return value.decode(charset, errors)
      except UnicodeError, e:
          if fallback is not None:
              return value.decode(fallback, 'replace')
          from werkzeug.exceptions import HTTPUnicodeError
          raise HTTPUnicodeError(str(e))