Accept up2date package parameter

lib/SlackBuilder/Trans.hs

@@ -1,11 +1,19 @@
 module SlackBuilder.Trans
-    ( SlackBuilderT(..)
+    ( SlackBuilderException(..)
+    , SlackBuilderT(..)
     ) where
 
 import Control.Monad.Trans.Reader (ReaderT(..))
+import Data.Text (Text)
 import SlackBuilder.Config
 import Control.Monad.IO.Class (MonadIO(..))
 import Control.Monad.Catch (MonadCatch(..), MonadThrow(..))
+import Control.Exception (Exception(..))
+
+newtype SlackBuilderException = UpdaterNotFound Text
+    deriving Show
+
+instance Exception SlackBuilderException
 
 newtype SlackBuilderT a = SlackBuilderT
     { runSlackBuilderT :: ReaderT Settings IO a