'Gets the capacity used by this drone
Returns a tuple of (percentage_full, -max_capacity). This is to aid
direct comparisons, so that a 0/10 drone is considered less heavily
loaded than a 0/2 drone.
This value should never be used directly. It should only be used in
direct comparisons using the basic comparison operators, or using the
cmp() function.'

def used_capacity(self):

    if (self.max_processes == 0):
        return (1.0, 0)
    return ((float(self.active_processes) / self.max_processes), (- self.max_processes))
