'Synchronously extract the result of the given L{Deferred}.  Fail the
test if that is not possible.'

def _extractDeferredResult(self, d):

    result = []
    error = []
    d.addCallbacks(result.append, error.append)
    if result:
        return result[0]
    elif error:
        error[0].raiseException()
    else:
        self.fail('Expected    result    not    available')
