If you are using AMQP there needs to be a ConnectionFactory (from
Spring Rabbit) in the application context. If there is a single
ConnectionFactory it will be used, or if there is a one qualified as
@[Hystrix,Turbine]ConnectionFactory it will be preferred over others,
otherwise the @Primary one will be used. If there are multiple
unqualified connection factories there will be an error.

See https://github.com/spring-cloud/spring-cloud-bus/issues/13