RESOURCE_MODIFIED is the only error here that is a system error not a user error. In other cases of this we show a generic message to the user that helps them understand the problem and tells them to retry. Below the error message is a code for further diagnosis. I think that is the right thing to do here but I'm not sure an easy way to implement it (so feel free to skip it). You can see how it's done here: https://github.com/mozilla/webpay/blob/master/webpay/base/utils.py#L41 (search for calls to ``system_error()``).