Show errors on stderr instead of stdout

Currently many of the exit and warning conditions mistakenly display error
messages on stdout, which makes parsing the output of programs harder. This
patch attempts to fix such occurrences.

Ganeti/HTools/CLI.hs

@@ -42,7 +42,7 @@ import System.IO
 import System.Info
 import System
 import Monad
-import Text.Printf (printf)
+import Text.Printf (printf, hPrintf)
 import qualified Data.Version
 
 import qualified Ganeti.HTools.Version as Version(version)
@@ -151,13 +151,13 @@ loadExternalData opts = do
       (case ldresult of
          Ok x -> return x
          Bad s -> do
-           printf "Error: failed to load data. Details:\n%s\n" s
+           hPrintf stderr "Error: failed to load data. Details:\n%s\n" s
            exitWith $ ExitFailure 1
       )
   let (fix_msgs, fixed_nl) = Loader.checkData loaded_nl il
 
   unless (null fix_msgs || silent opts) $ do
-         putStrLn "Warning: cluster has inconsistent data:"
-         putStrLn . unlines . map (printf "  - %s") $ fix_msgs
+         hPutStrLn stderr "Warning: cluster has inconsistent data:"
+         hPutStrLn stderr . unlines . map (printf "  - %s") $ fix_msgs
 
   return (fixed_nl, il, csf)

hail.hs

@@ -124,7 +124,7 @@ main = do
 
   request <- case (parseData input_data) of
                Bad err -> do
-                 putStrLn $ "Error: " ++ err
+                 hPutStrLn stderr $ "Error: " ++ err
                  exitWith $ ExitFailure 1
                Ok rq -> return rq
 

hbal.hs

@@ -34,7 +34,7 @@ import System.IO
 import System.Console.GetOpt
 import qualified System
 
-import Text.Printf (printf)
+import Text.Printf (printf, hPrintf)
 
 import qualified Ganeti.HTools.Container as Container
 import qualified Ganeti.HTools.Cluster as Cluster
@@ -224,8 +224,8 @@ main = do
       m_dsk = optMdsk opts
 
   when (length offline_wrong > 0) $ do
-         printf "Wrong node name(s) set as offline: %s\n"
-                (commaJoin offline_wrong)
+         hPrintf stderr "Wrong node name(s) set as offline: %s\n"
+                     (commaJoin offline_wrong)
          exitWith $ ExitFailure 1
 
   let nm = Container.map (\n -> if elem (Node.idx n) offline_indices

hspace.hs

@@ -33,7 +33,7 @@ import System.IO
 import System.Console.GetOpt
 import qualified System
 
-import Text.Printf (printf)
+import Text.Printf (printf, hPrintf)
 
 import qualified Ganeti.HTools.Container as Container
 import qualified Ganeti.HTools.Cluster as Cluster
@@ -241,14 +241,15 @@ main = do
          hPutStrLn stderr "Error: this program doesn't take any arguments."
          exitWith $ ExitFailure 1
 
+  let verbose = optVerbose opts
+
+  (fixed_nl, il, csf) <- CLI.loadExternalData opts
+
   printf "Spec RAM: %d\n" (optIMem opts)
   printf "Spec disk: %d\n" (optIDsk opts)
   printf "Spec CPUs: %d\n" (optIVCPUs opts)
   printf "Spec nodes: %d\n" (optINodes opts)
 
-  let verbose = optVerbose opts
-
-  (fixed_nl, il, csf) <- CLI.loadExternalData opts
   let num_instances = length $ Container.elems il
 
   let offline_names = optOffline opts
@@ -263,12 +264,12 @@ main = do
       m_dsk = optMdsk opts
 
   when (length offline_wrong > 0) $ do
-         printf "Error: Wrong node name(s) set as offline: %s\n"
-                (commaJoin offline_wrong)
+         hPrintf stderr "Error: Wrong node name(s) set as offline: %s\n"
+                     (commaJoin offline_wrong)
          exitWith $ ExitFailure 1
 
   when (req_nodes /= 1 && req_nodes /= 2) $ do
-         printf "Error: Invalid required nodes (%d)\n" req_nodes
+         hPrintf stderr "Error: Invalid required nodes (%d)\n" req_nodes
          exitWith $ ExitFailure 1
 
   let nm = Container.map (\n -> if elem (Node.idx n) offline_indices