fixed misuse of template variable

cmd/minikube/cmd/start.go

@@ -210,7 +210,7 @@ func runStart(cmd *cobra.Command, args []string) {
 		if viper.GetBool(createMount) {
 			mount := viper.GetString(mountString)
 			if len(existing.ContainerVolumeMounts) != 1 || existing.ContainerVolumeMounts[0] != mount {
-				out.WarningT("Due to the limitations of %s, it's not possible to change mount configuration of an existing cluster.", out.V{"driver": existing.Driver})
+				out.WarningT("Due to the limitations of {{.driver}}, it's not possible to change mount configuration of an existing cluster.", out.V{"driver": existing.Driver})
 				out.WarningT("If necessary delete and recreate the cluster, proceeding with old mount configuration")
 			}
 		}