follow change of directory layout of the HackageDB data

cabal-install/src/Network/Hackage/CabalInstall/Fetch.hs

@@ -107,6 +107,7 @@ downloadIndex cfg serv
 packageFile :: ConfigFlags -> PackageIdentifier -> FilePath
 packageFile cfg pkg = packagesDirectory cfg 
                       </> pkgName pkg
+                      </> showVersion (pkgVersion pkg)
                       </> showPackageId pkg 
                       <.> "tar.gz"
 
@@ -146,4 +147,4 @@ fetch cfg pkgs
           output = configOutputGen cfg
 
 withBinaryFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r
-withBinaryFile name mode = bracket (openBinaryFile name mode) hClose
\ No newline at end of file
+withBinaryFile name mode = bracket (openBinaryFile name mode) hClose