[i18n-activity] Message text not localizable

aphillips has just created a new issue for https://github.com/w3c/i18n-activity:

== Message text not localizable ==
http://w3c.github.io/webrtc-pc/#rtcpeerconnectioniceerrorevent

Error values can contain an attribute:

```
    readonly attribute USVString      errorText;
```

This appears to use the text defined [here](https://www.iana.org/assignments/stun-parameters/stun-parameters.xhtml#stun-parameters-6) and doesn't allow for localization of the error message. Shouldn't it allow for localization (complete with language and bidi support)

Please view or discuss this issue at https://github.com/w3c/i18n-activity/issues/377 using your GitHub account