AR::UnknownAttributeError should include the class name of a record

This would be helpful if 2 models have an attribute that has a similar
name to the other. e.g:

before:

    User.new(name: "Yuki Nishijima", projects_attributes: [name: "kaminari"])
    # => ActiveRecord::UnknownAttributeError: unknown attribute: name

after:

    User.new(name: "Yuki Nishijima", projects_attributes: [name: "kaminari"])
    # => ActiveRecord::UnknownAttributeError: unknown attribute on User: name

1 files changed, 1 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 52c70977ef..2b9b3c8f73 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -167,7 +167,7 @@ module ActiveRecord
     def initialize(record, attribute)
       @record = record
       @attribute = attribute.to_s
-      super("unknown attribute: #{attribute}")
+      super("unknown attribute on #{@record.class}: #{attribute}")
     end
 
   end