Fix older GHCs

Language/Haskell/GhcMod/Gap.hs

@@ -42,6 +42,7 @@ module Language.Haskell.GhcMod.Gap (
   , lookupModulePackageInAllPackages
   , Language.Haskell.GhcMod.Gap.isSynTyCon
   , parseModuleHeader
+  , mkErrStyle'
   ) where
 
 import Control.Applicative hiding (empty)
@@ -559,3 +560,10 @@ parseModuleHeader str dflags filename =
      POk pst rdr_module ->
          let (warns,_) = getMessages pst in
          Right (warns, rdr_module)
+
+mkErrStyle' :: DynFlags -> PrintUnqualified -> PprStyle
+#if __GLASGOW_HASKELL__ >= 706
+mkErrStyle' = Outputable.mkErrStyle
+#else
+mkErrStyle' _ = Outputable.mkErrStyle
+#endif

Language/Haskell/GhcMod/Logger.hs

@@ -134,7 +134,7 @@ ppErrMsg :: ErrMsg -> GmPprEnvM String
 ppErrMsg err = do
     dflags <- asks gpeDynFlags
     let unqual = errMsgContext err
-        st = mkErrStyle dflags unqual
+        st = Gap.mkErrStyle' dflags unqual
     let ext = showPage dflags st (errMsgExtraInfo err)
     m <- ppMsg st spn SevError msg
     return $ m ++ (if null ext then "" else "\n" ++ ext)