How are errors handled in RPC calls?
All RPC calls are assumed to succeed. Errors are never part of the normal return values. Instead, if a RPC call generates an error a seperate callback is invoked known as the errback. Thus when calling an RPC method you may attach a normal callback to it and/or a callback to handle an error, the two are distinct. When the RPC returns either the attached callbacks are going to be invoked if it is successful or the attached errbacks are going to be invoked if it failed.
