terraform: register gob type that might be in config

command/test-fixtures/plan/main.tf

@@ -1,6 +1,7 @@
 resource "test_instance" "foo" {
     ami = "bar"
 
+    # This is here because at some point it caused a test failure
     network_interface {
       device_index = 0
       description = "Main network interface"

terraform/plan.go

@@ -11,6 +11,10 @@ import (
 	"github.com/hashicorp/terraform/config"
 )
 
+func init() {
+	gob.Register(make([]map[string]interface{}, 0))
+}
+
 // PlanOpts are the options used to generate an execution plan for
 // Terraform.
 type PlanOpts struct {