XML error responses are not compatible with ActiveResource.

[nasa42]

Chargify API returns errors in following XML format:

<?xml version="1.0" encoding="UTF-8"?>
<errors type="array">
  <error>One or more allocation changes are required.</error>
</errors>

Which is converted to following Hash:

{ "errors" => ["One or more allocation changes are required."] }

But that causes a TypeError at line 75 in validation.rb, and ActiveResource swallows the exception and returns an empty errors array to app.