gf3 should not exit if there is a syntax error in the file

src/GF/Command/Importing.hs

@@ -6,15 +6,22 @@ import GF.GFCC.API
 
 import GF.Devel.UseIO
 import GF.Infra.Option
+import GF.Data.ErrM
 
 import Data.List (nubBy)
 
 -- import a grammar in an environment where it extends an existing grammar
 importGrammar :: MultiGrammar -> Options -> [FilePath] -> IO MultiGrammar
-importGrammar mgr0 opts files = do
-  gfcc2 <- case fileSuffix (last files) of
-    s | elem s ["gf","gfo"] -> compileToGFCC opts files
-    "gfcc" -> 
-      mapM file2gfcc files >>= return . foldl1 unionGFCC
-  let gfcc3 = unionGFCC (gfcc mgr0) gfcc2
-  return $ MultiGrammar gfcc3
+importGrammar mgr0 opts files =
+  case fileSuffix (last files) of
+    s | elem s ["gf","gfo"] -> do
+      res <- appIOE $ compileToGFCC opts files
+      case res of
+        Ok gfcc2 -> do let gfcc3 = unionGFCC (gfcc mgr0) gfcc2
+                       return $ MultiGrammar gfcc3
+        Bad msg  -> do print msg
+                       return mgr0
+    "gfcc" -> do
+      gfcc2 <- mapM file2gfcc files >>= return . foldl1 unionGFCC
+      let gfcc3 = unionGFCC (gfcc mgr0) gfcc2
+      return $ MultiGrammar gfcc3