fix the testsuite failure after the second run

src/runtime/haskell/pgf2.cabal

@@ -51,4 +51,5 @@ test-suite basic
     base,
     HUnit,
     random,
+    directory,
     pgf2

src/runtime/haskell/tests/basic.hs

@@ -1,4 +1,5 @@
 import System.Random
+import System.Directory
 import Control.Exception
 import Test.HUnit
 import PGF2
@@ -69,6 +70,9 @@ main = do
       ,TestCase (assertEqual "unicode names 4" (Just "'а\\'б'") (fmap (showExpr []) (readExpr "'а\\'б'")))
       ]
 
+  removeFile "tests/basic.ngf" `catch` \e -> do
+    print (e :: SomeException)
+
   gr1 <- readPGF "tests/basic.pgf"
   gr2 <- bootNGF "tests/basic.pgf" "tests/basic.ngf"
   gr3 <- readNGF "tests/basic.ngf"