Properly require ActiveModel validation dependencies

activemodel/lib/active_model/errors.rb

@@ -1,3 +1,5 @@
+require 'active_support/core_ext/string/inflections'
+
 module ActiveModel
   class Errors < Hash
     include DeprecatedErrorMethods

activemodel/lib/active_model/validations.rb

@@ -1,3 +1,6 @@
+require 'active_support/core_ext/array/extract_options'
+require 'active_support/core_ext/hash/keys'
+
 module ActiveModel
   module Validations
     extend ActiveSupport::Concern
@@ -69,7 +72,6 @@ module ActiveModel
       end
 
       private
-
         def validation_method(on)
           :validate
         end

activemodel/lib/active_model/validations/presence.rb

@@ -1,3 +1,5 @@
+require 'active_support/core_ext/object/blank'
+
 module ActiveModel
   module Validations
     module ClassMethods