List VMS for an engine

def list(self, engine):
        """
        List VMS for an engine
        """
        engine = self._get_engine(engine)
        vms = []
        try:
            for vm in (yield from engine.list()):
                vms.append({"vmname": vm["vmname"]})
        except GNS3VMError as e:
            # We raise error only if user activated the GNS3 VM
            # otherwise you have noise when VMware is not installed
            if self.enable:
                raise e
        return vms