Comment 1 for bug 1881596

Same here,
https://pastebin.ubuntu.com/p/zHzkhkkmYc/

2020-07-17 12:05:27 DEBUG shared-db-relation-departed Traceback (most recent call last):
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/charm/hooks/shared-db-relation-departed", line 22, in <module>
2020-07-17 12:05:27 DEBUG shared-db-relation-departed main()
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/.venv/lib/python3.8/site-packages/charms/reactive/__init__.py", line 74, in main
2020-07-17 12:05:27 DEBUG shared-db-relation-departed bus.dispatch(restricted=restricted_mode)
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 390, in dispatch
2020-07-17 12:05:27 DEBUG shared-db-relation-departed _invoke(other_handlers)
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 359, in _invoke
2020-07-17 12:05:27 DEBUG shared-db-relation-departed handler.invoke()
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 181, in invoke
2020-07-17 12:05:27 DEBUG shared-db-relation-departed self._action(*args)
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/charm/reactive/mysql_router_handlers.py", line 102, in proxy_shared_db_responses
2020-07-17 12:05:27 DEBUG shared-db-relation-departed instance.proxy_db_and_user_responses(db_router, shared_db)
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "lib/charm/openstack/mysql_router.py", line 481, in proxy_db_and_user_responses
2020-07-17 12:05:27 DEBUG shared-db-relation-departed unit = sending_interface.all_joined_units[0]
2020-07-17 12:05:27 DEBUG shared-db-relation-departed File "/var/lib/juju/agents/unit-keystone-mysql-router-0/.venv/lib/python3.8/site-packages/charms/reactive/endpoints.py", line 582, in __getitem__
2020-07-17 12:05:27 DEBUG shared-db-relation-departed return super().__getitem__(self._translate_key(key))
2020-07-17 12:05:27 DEBUG shared-db-relation-departed IndexError: list index out of range