module AWS::S3::Client::Validators

def require_acl!(acl)
  validate!('acl', acl) do
    case
    when acl.kind_of?(Hash)
      AccessControlList.new(acl).validate!
      nil
    when !acl.respond_to?(:to_str) && !acl.respond_to?(:to_xml)
      "must support to_xml: #{acl.inspect}"
    when acl.nil? || acl == ''
      'may not be blank'
    else
      xml_validation_message(acl)
    end
  end
end