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

[Phil Mayers]

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?