[Twisted-Python] t.w.client.Agent exceptions

All, I'm having a head-poundingly annoying time getting detailed exception info out of the new Agent stuff. Specifically, I have some bug inside my code somewhere, but I can't get decent tracebacks out because _WrapperException is the base class for RequestGenerationFailed, but there's no public (non-underscore-prefixed) way to get that. It seems like an API error; how is one supposed to err.track/check other than importing a non-public API?