code: func TooLong(field *Path, value interface{}, maxLength int) *Error {
  	return &Error{ErrorTypeTooLong, field.String(), value, fmt.Sprintf("must have at most %d characters", maxLength)}
  }
docs: // TooLong returns a *Error indicating "too long".  This is used to
  // report that the given value is too long.  This is similar to
  // Invalid, but the returned error will not include the too-long
  // value.