module Devise::Models::Validatable

def self.included(base)
  base.extend ClassMethods
  assert_validations_api!(base)
  base.class_eval do
    validates_presence_of   :email, if: :email_required?
    validates_uniqueness_of :email, allow_blank: true, case_sensitive: true, if: :devise_will_save_change_to_email?
    validates_format_of     :email, with: email_regexp, allow_blank: true, if: :devise_will_save_change_to_email?
    validates_presence_of     :password, if: :password_required?
    validates_confirmation_of :password, if: :password_required?
    validates_length_of       :password, within: password_length, allow_blank: true
  end
end