'Verify that the rate hasn\'t decreased and that the scenario is
not overloaded. A scenario is overloaded if there are too many
outstanding requests.
:raise RequestRateTooLow: if the rate has dropped.
:raise RequestOverload: if the scenario is overloaded.'

def check_rate(self):

    rate = self.rate_measurer.rate()
    if (rate < self.rate_tolerated):
        self._fail(RequestRateTooLow(rate))
    elif (self.rate_measurer.num_of_erros() >= self.tolerated_errors):
        self._fail(RequestRateTooLow(rate))
    elif (self.rate_measurer.outstanding() > self.max_outstanding):
        self._fail(RequestOverload())
