Fix backwards-compatibility

Author: Lennart Spitzner

cabal-install/Distribution/Client/Status.hs

@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Distribution.Client.Status
@@ -77,14 +79,17 @@ import qualified Distribution.Simple.LocalBuildInfo as LBI
 
 import qualified Paths_cabal_install          ( version )
 
-import System.Environment                     ( getExecutablePath )
+import Distribution.Client.Compat.ExecutablePath ( getExecutablePath )
 import System.Directory                       ( doesFileExist )
 import System.FilePath                        ( splitFileName
                                               , combine
                                               , splitPath
                                               , joinPath
                                               , takeDirectory
                                               )
+#if !MIN_VERSION_base(4,8,0)
+import Data.Functor                           ( (<$) )
+#endif
 import Control.Monad                          ( when
                                               , forM
                                               , guard
@@ -94,8 +99,10 @@ import Data.Version                           ( showVersion
                                               )
 import Data.Maybe                             ( isJust
                                               )
-import Data.List                              ( sortOn
-                                              , groupBy
+import Data.List                              ( groupBy
+                                              , sortBy
+                                              )
+import Data.Ord                               ( comparing
                                               )
 import Text.PrettyPrint                       ( empty
                                               , ($$)
@@ -106,7 +113,11 @@ import Text.PrettyPrint                       ( empty
                                               , ($+$)
                                               , (<+>)
                                               )
-import Data.Monoid                            ( (<>) )
+import Data.Monoid                            ( (<>)
+#if !MIN_VERSION_base(4,8,0)
+                                              , mappend
+#endif
+                                              )
 import Data.List                              ( inits )
 import Data.Foldable                          ( asum )
 
@@ -307,7 +318,9 @@ status verbosity globalFlags statusFlags = do
     installedPackageIndex <- getInstalledPackages verbosity comp dbs conf
     let pkgs = allPackages installedPackageIndex
         pkgTuples = [ (root, disp $ sourcePackageId pkg) | pkg <- pkgs, root <- [x | Just x <- [pkgRoot pkg]]]
-        grouped = groupBy (\a b -> fst a == fst b) $ sortOn fst pkgTuples
+        grouped = groupBy (\a b -> fst a == fst b)
+                $ sortBy (comparing fst)
+                $ pkgTuples
         groups = [(fst (head x), map snd x) | x <- grouped]
     let packageDoc ps = if    Cabal.fromFlag (statusPackages statusFlags)
                            || Cabal.fromFlag (statusAll statusFlags)