VariantOverrides require hub and variant

app/models/variant_override.rb

@@ -1,6 +1,8 @@
 class VariantOverride < ActiveRecord::Base
-  belongs_to :variant, class_name: 'Spree::Variant'
   belongs_to :hub, class_name: 'Enterprise'
+  belongs_to :variant, class_name: 'Spree::Variant'
+
+  validates_presence_of :hub_id, :variant_id
 
   scope :for_hubs, lambda { |hubs|
     where(hub_id: hubs)

db/migrate/20141210233407_add_not_null_to_variant_override_relations.rb

@@ -0,0 +1,6 @@
+class AddNotNullToVariantOverrideRelations < ActiveRecord::Migration
+  def change
+    change_column :variant_overrides, :hub_id, :integer, null: false
+    change_column :variant_overrides, :variant_id, :integer, null: false
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20141113053004) do
+ActiveRecord::Schema.define(:version => 20141210233407) do
 
   create_table "adjustment_metadata", :force => true do |t|
     t.integer "adjustment_id"
@@ -1034,8 +1034,8 @@ ActiveRecord::Schema.define(:version => 20141113053004) do
   end
 
   create_table "variant_overrides", :force => true do |t|
-    t.integer "variant_id"
-    t.integer "hub_id"
+    t.integer "variant_id",                                  :null => false
+    t.integer "hub_id",                                      :null => false
     t.decimal "price",         :precision => 8, :scale => 2
     t.integer "count_on_hand"
   end