Prefix the method name with the class name

instance.errors.full_messages will now produce something like:
["SomeClass: The method can't be blank"]

app/models/application_record.rb

@@ -23,4 +23,8 @@ class ApplicationRecord < ActiveRecord::Base
   def self.display_name(number = 1)
     n_(model_name.singular.titleize, model_name.plural.titleize, number)
   end
+
+  def self.human_attribute_name(attribute, *args)
+    "#{name}: #{super}"
+  end
 end

spec/models/application_record_spec.rb

@@ -0,0 +1,13 @@
+describe ApplicationRecord do
+  context ".human_attribute_name puts the class name in the validation error" do
+    it "single level" do
+      Zone.create!(:name => "example", :description => "example")
+      expect { Zone.create!(:name => "example", :description => "example") }.to raise_error(ActiveRecord::RecordInvalid, "Validation failed: Zone: Name is not unique within region #{MiqRegion.my_region_number}")
+    end
+
+    it "nested" do
+      Zone.create!(:name => "example", :description => "example")
+      expect { MiqSchedule.create!(:zone => Zone.create!(:name => "example", :description => "example")) }.to raise_error(ActiveRecord::RecordInvalid, "Validation failed: Zone: Name is not unique within region #{MiqRegion.my_region_number}")
+    end
+  end
+end