Release the lock.

            Removes the PID file to release the lock, or raises an
            error if the current process does not hold the lock.

def release(self):
        """ Release the lock.

            Removes the PID file to release the lock, or raises an
            error if the current process does not hold the lock.

            """
        if not self.is_locked():
            raise NotLocked("%s is not locked" % self.path)
        if not self.i_am_locking():
            raise NotMyLock("%s is locked, but not by me" % self.path)
        remove_existing_pidfile(self.path)