Comment 3 for bug 1793364

My guess is the IndexError is coming from the this:

connection.scalar(select([1]))

In this part of the stacktrace:

2018-09-19 15:33:46.805287 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/event/attr.py", line 256, in __call__
2018-09-19 15:33:46.805351 | ubuntu-xenial | fn(*args, **kw)
2018-09-19 15:33:46.805522 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/oslo_db/sqlalchemy/engines.py", line 73, in _connect_ping_listener
2018-09-19 15:33:46.805608 | ubuntu-xenial | connection.scalar(select([1]))
2018-09-19 15:33:46.805775 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 880, in scalar
2018-09-19 15:33:46.805868 | ubuntu-xenial | return self.execute(object, *multiparams, **params).scalar()
2018-09-19 15:33:46.806028 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/result.py", line 1233, in scalar
2018-09-19 15:33:46.806085 | ubuntu-xenial | row = self.first()
2018-09-19 15:33:46.806216 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/result.py", line 1207, in first
2018-09-19 15:33:46.806273 | ubuntu-xenial | return self._non_result(None)
2018-09-19 15:33:46.806446 | ubuntu-xenial | File "/home/zuul/src/git.openstack.org/openstack/nova/.tox/py27/local/lib/python2.7/site-packages/sqlalchemy/engine/result.py", line 1089, in _non_result
2018-09-19 15:33:46.806530 | ubuntu-xenial | "This result object does not return rows. "
2018-09-19 15:33:46.806661 | ubuntu-xenial | sqlalchemy.exc.ResourceClosedError: This result object does not return rows. It has been closed automatically.