'Remove the lock.
Note that this only resets the lock if we actually hold it since
lock_expiration == self.expires and lock_owner = self.lock_token.'

def Release(self):

    if self.locked:
        query = 'UPDATE    locks    SET    lock_expiration=0,    lock_owner=0    WHERE    lock_expiration=%s    AND    lock_owner=%s    AND    subject_hash=unhex(md5(%s))'
        args = [self.expires, self.lock_token, self.subject]
        self.store.ExecuteQuery(query, args)
        self.locked = False
