When migrating a model from one Azure controller to another, the sanity check fails because there's an instance named 'common' that doesn't correspond to a machine in the model.
2017-08-23 06:13:10 INFO juju.worker.migrationmaster.0712d2 worker.go:275 checking machines in migrated model
2017-08-23 06:13:11 ERROR juju.worker.migrationmaster.0712d2 worker.go:472 no machine with instance "common"
2017-08-23 06:13:11 ERROR juju.worker.migrationmaster.0712d2 worker.go:279 machine sanity check failed, 1 error found
2017-08-23 06:13:11 INFO juju.worker.migrationmaster.0712d2 worker.go:249 setting migration phase to ABORT
2017-08-23 06:13:11 INFO juju.worker.migrationmaster.0712d2 worker.go:275 aborted, removing model from target controller
Not sure where the common instance is coming from, probably it just needs to be in an allow-list.
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