Canada: process custom HTTP response errors.

Fixes #3480.

![image](https://cloud.githubusercontent.com/assets/672669/5185275/cbf6f9b8-74c6-11e4-8e1e-49a7fe97cb6b.png)
![image](https://cloud.githubusercontent.com/assets/672669/5185299/06e5d260-74c7-11e4-9965-0669f249b444.png)