squash! Hackport.Env: Fix warnings message

Use 'unless' from Control.Monad

Give more explicit imports to help with compatibility between major GHC
versions. This requires some tweaking to imports in other files.

src/Hackport/Env.hs

@@ -28,6 +28,7 @@ module Hackport.Env
   , WritesMetadata (..)
   , UseHackageRemote
     -- * Re-exports
+  , module Control.Monad.IO.Class
   , module Control.Monad.Reader
   ) where
 

src/Overlays.hs

@@ -14,7 +14,7 @@ import System.FilePath ((</>), splitPath, joinPath)
 import Error
 import Portage.Host
 import Util (info)
-import Hackport.Env hiding (local)
+import Hackport.Env
 
 -- getOverlayPath :: forall m. (HasGlobalEnv m, MonadIO m) => m String
 getOverlayPath :: Env env String