Exception information is lost when using RemoteTransport

_translate_error re-raises exceptions without including all the information that was in the original exception. e.g. if it receives a NoSuchFile error in the response, it will re-raise it as a NoSuchFile error, but with the 'path' or 'extras' parameters that were provided when the original exception was raised.

I don't know if this is a protocol issue or just a bug with _translate_error. Either way, it would be good to have it fixed. My use case is wanting to provide informative error messages to people using Launchpad codehosting.