Update london postcode validation error message

app/models/validations/property_validations.rb

@@ -58,7 +58,7 @@ module Validations::PropertyValidations
     if record.la.present? && !LONDON_BOROUGHS.include?(record.la) && record.is_london_rent?
       record.errors.add :la, I18n.t("validations.property.la.london_rent")
       if record.postcode_known? && record.property_postcode.present?
-        record.errors.add :property_postcode, I18n.t("validations.property.la.london_rent")
+        record.errors.add :property_postcode, I18n.t("validations.property.la.london_rent_postcode")
       end
     end
 

config/locales/en.yml

@@ -61,6 +61,7 @@ en:
         relet_number: "Property number of times relet must be between 0 and 20"
       la:
         london_rent: "Local authority has to be in London"
+        london_rent_postcode: "The postcode must be a London postcode because you told us the rent type is London Affordable Rent or London Living Rent"
         la_known: "Enter a local authority"
       rsnvac:
         first_let_not_social: "Reason for vacancy cannot be first let if unit has been previously let as social housing"

spec/models/validations/property_validations_spec.rb

@@ -167,6 +167,8 @@ RSpec.describe Validations::PropertyValidations do
       end
 
       context "when the la has been derived from a known postcode" do
+        let(:expected_error) { I18n.t("validations.property.la.london_rent_postcode") }
+
         it "also adds an error to the postcode field" do
           record.la = "E07000105"
           record.rent_type = 2