'can verify that a location exists, using ccx block usage key'

def test_has_item(self):

    for item in chain(self.chapters, self.sequentials, self.verticals, self.blocks):
        block_key = self.ccx_locator.make_usage_key(item.location.block_type, item.location.block_id)
        self.assertTrue(self.store.has_item(block_key))
