'Print tracebacks and die.
If the *last* (and I do mean *last*) callback leaves me in an error
state, print a traceback (if said errback is a L{Failure}).'

def __del__(self):

    if (self.failResult is not None):
        log.critical('Unhandled    error    in    Deferred:', isError=True)
        debugInfo = self._getDebugTracebacks()
        if debugInfo:
            format = '(debug:    {debugInfo})'
        else:
            format = None
        log.failure(format, self.failResult, debugInfo=debugInfo)
