Revert "Remove custom error message"

This reverts commit bd3887a5e1.

app/models/validations/sales/sale_information_validations.rb

@@ -356,6 +356,18 @@ module Validations::Sales::SaleInformationValidations
     end
   end
 
+  def validate_number_of_staircase_transactions(record)
+    return unless record.numstair
+
+    if record.firststair == 1 && record.numstair >= 2 || record.firststair != 1 && record.numstair == 1
+      record.errors.add :numstair, I18n.t("validations.sales.sale_information.numstair.must_be_greater_than_one")
+      record.errors.add :firststair, I18n.t("validations.sales.sale_information.firststair.more_than_one_transaction")
+    end
+    if record.numstair > 10
+      record.errors.add :numstair, I18n.t("validations.sales.sale_information.numstair.must_be_ten_or_less")
+    end
+  end
+
   def over_tolerance?(expected, actual, tolerance, strict: false)
     if strict
       (expected - actual).abs > tolerance