Add exception related functionality.

postlude.cabal

@@ -20,6 +20,7 @@ library
   build-depends:       base >= 4.7 && < 5,
                        bytestring == 0.10.8.1,
                        either == 4.4.1.1,
+                       exceptions == 0.8.3,
                        free == 4.12.4,
                        mtl == 2.2.1,
                        text == 1.2.2.2,

src/Postlude.hs

@@ -33,6 +33,22 @@ import Control.Monad as X
   , guard
   )
 
+import Control.Monad.Catch as X
+  ( Exception
+  ,   Exception(displayException)
+  ,   Exception(fromException)
+  ,   Exception(toException)
+  , Handler, Handler(Handler)
+  , MonadCatch, catch
+  , MonadMask, mask, uninterruptibleMask
+  , MonadThrow, throwM
+  , SomeException, SomeException(SomeException)
+  , bracket
+  , finally
+  , handle
+  , try
+  )
+
 import Control.Monad.Except as X
   -- Note runExceptT is not actually a type declaration within the ExceptT
   -- newtype but writing as follows for consistency's sake.