some error handling and cleanup that comes with it

app/Monad.hs

@@ -0,0 +1,36 @@
+{-# LANGUAGE GeneralisedNewtypeDeriving #-}
+module Monad(
+    App
+  ,module Control.Monad.Fail
+  ,module Control.Monad.IO.Class
+  ,throwE
+  ,except
+  ,runApp
+  ) where
+  
+import qualified Control.Monad.Trans.Except as T
+import Control.Monad.Fail
+import Control.Monad.IO.Class
+
+
+-- We need this type isomorphism, because we want a different
+-- MonadFail implementation, if someone knows how to do this
+-- without writing the isomorphism out explicitly for all
+-- the other instances, (or without scary GeneralisedNewtypeDeriving)
+--  I would be happy
+newtype App a = App { runApp' :: T.ExceptT String IO a}
+  deriving (Functor, Applicative, Monad, MonadIO)
+
+instance MonadFail App where
+  fail = throwE
+
+-- reimplementing ExceptT interface
+-- I would love not to have to do this but I don't know how
+throwE :: String -> App a
+throwE = App . T.throwE
+
+except :: Either String a -> App a
+except = App . T.except
+
+runApp :: App a -> IO (Either String a)
+runApp = T.runExceptT . runApp'