def addErrback(self, errback, *args, **kw):
        return self.addCallbacks(_passthrough, errback, errbackArgs=args,
                                 errbackKeywords=kw)
Add a failure callback that will be run in the context of an eliot
dataset/ETHPy150Open ClusterHQ/eliot/eliot/twisted.py/DeferredContext.addErrback