def __delitem__(self, i):
        list.__delitem__(self, i)
        self.changed()
L{SSHPublicKeyDatabase.checkKey} should retrieve the content of the
dataset/ETHPy150Open openstack/sahara/sahara/db/sqlalchemy/types.py/MutableList.__delitem__--crossover with--dataset/ETHPy150Open twisted/twisted/twisted/conch/test/test_checkers.py/SSHPublicKeyDatabaseTests.test_checkKey2