This is a failure I get in nova-conductor without having [database]/connection set:

http://logs.openstack.org/46/555346/3/check/tempest-full/d4a85cf/controller/logs/screen-n-super-cond.txt.gz?level=TRACE#_Mar_27_01_15_28_067478

Mar 27 01:15:28.067478 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service [None req-1307238b-460a-475f-8617-3ef1a8cc9454 None None] Error starting thread.: ArgumentError: Could not parse rfc1738 URL from string 'None'
Mar 27 01:15:28.067623 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service Traceback (most recent call last):
Mar 27 01:15:28.067750 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_service/service.py", line 729, in run_service
Mar 27 01:15:28.067877 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     service.start()
Mar 27 01:15:28.068003 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/opt/stack/nova/nova/service.py", line 166, in start
Mar 27 01:15:28.068136 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     ctxt, self.host, self.binary)
Mar 27 01:15:28.068261 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_versionedobjects/base.py", line 184, in wrapper
Mar 27 01:15:28.068405 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     result = fn(cls, context, *args, **kwargs)
Mar 27 01:15:28.068536 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/opt/stack/nova/nova/objects/service.py", line 314, in get_by_host_and_binary
Mar 27 01:15:28.068662 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     host, binary)
Mar 27 01:15:28.068787 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/opt/stack/nova/nova/db/api.py", line 127, in service_get_by_host_and_binary
Mar 27 01:15:28.068925 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     return IMPL.service_get_by_host_and_binary(context, host, binary)
Mar 27 01:15:28.069055 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/opt/stack/nova/nova/db/sqlalchemy/api.py", line 239, in wrapped
Mar 27 01:15:28.069175 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     with ctxt_mgr.reader.using(context):
Mar 27 01:15:28.069298 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
Mar 27 01:15:28.069412 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     return self.gen.next()
Mar 27 01:15:28.069532 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 1041, in _transaction_scope
Mar 27 01:15:28.069651 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     context=context) as resource:
Mar 27 01:15:28.069771 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
Mar 27 01:15:28.069900 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     return self.gen.next()
Mar 27 01:15:28.070020 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 644, in _session
Mar 27 01:15:28.070140 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     bind=self.connection, mode=self.mode)
Mar 27 01:15:28.070286 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 408, in _create_session
Mar 27 01:15:28.070409 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     self._start()
Mar 27 01:15:28.070542 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 495, in _start
Mar 27 01:15:28.070663 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     engine_args, maker_args)
Mar 27 01:15:28.070782 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 519, in _setup_for_connection
Mar 27 01:15:28.070911 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     sql_connection=sql_connection, **engine_kwargs)
Mar 27 01:15:28.071034 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/debtcollector/renames.py", line 43, in decorator
Mar 27 01:15:28.071156 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     return wrapped(*args, **kwargs)
Mar 27 01:15:28.071278 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/engines.py", line 153, in create_engine
Mar 27 01:15:28.071400 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     url = sqlalchemy.engine.url.make_url(sql_connection)
Mar 27 01:15:28.071528 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 211, in make_url
Mar 27 01:15:28.071650 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     return _parse_rfc1738_args(name_or_url)
Mar 27 01:15:28.071782 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 270, in _parse_rfc1738_args
Mar 27 01:15:28.071904 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service     "Could not parse rfc1738 URL from string '%s'" % name)
Mar 27 01:15:28.072023 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service ArgumentError: Could not parse rfc1738 URL from string 'None'
Mar 27 01:15:28.072143 ubuntu-xenial-ovh-bhs1-0003203353 nova-conductor[12477]: ERROR oslo_service.service