Change behaviour of Spree::Address.build_default

Instead of the first country found, please raise an error if
the default country ISO code does not have an associated country.

The issue referenced in the spec, spree/spree#1142,
is people complaining about no states found for Nil, which only ever
happened because Spree::Country.default would silently fail before.

core/spec/models/spree/address_spec.rb

@@ -165,18 +165,20 @@
 
  context 'has a default country' do
  before do
- Spree::Config[:default_country_id] = default_country.id
+ Spree::Config[:default_country_iso] = default_country.iso
  end
 
- it "sets up a new record with Spree::Config[:default_country_id]" do
+ it "sets up a new record with Spree::Config[:default_country_iso]" do
  expect(Spree::Address.build_default.country).to eq default_country
  end
  end
 
  # Regression test for https://github.com/spree/spree/issues/1142
- it "uses the first available country if :default_country_id is set to an invalid value" do
- Spree::Config[:default_country_id] = "0"
- expect(Spree::Address.build_default.country).to eq default_country
+ it "raises ActiveRecord::RecordNotFound if :default_country_iso is set to an invalid value" do
+ Spree::Config[:default_country_iso] = "00"
+ expect {
+ Spree::Address.build_default.country
+ }.to raise_error(ActiveRecord::RecordNotFound)
  end
  end
  end