Before it works, I had to add these lines: <service name="RM"/> <service name="CPU"/> <service name="IO_PORT"/> <service name="IRQ"/> inside <parent-provides> section of hello.run.
I would have tought however that: <default-route> <any-service> <parent/> <any-child/> </any-service> </default-route> would have made it optional, which was not.