The error responses from the API are often shown in languages other than English, seemingly random. For example:

Started POST "/api/smart_proxies" for 10.35.160.133 at 2013-12-05
17:01:27 +0200
Processing by Api::V1::SmartProxiesController#create as JSON
   Parameters:
{"smart_proxy"=>{"url"=>"https://example.redhat.com:9090",
"name"=>"example.redhat.com"}}
Authorized user admin(Admin User)
Unprocessable entity SmartProxy (id: new):
   No ha sido posible establecer una comunicación con el proxy:
SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B:
certificate verify failed
   Por favor, comprueba que el proxy está configurado y ejecutándose en
el equipo

I suspect we're not initialising the current locale correctly in the API controllers, while we do in the UI controllers based on the user.

(https://bugzilla.redhat.com/show_bug.cgi?id=1039011)