Minor improvements to CardGenerator and the corresponding unit test

Make sure that the file gets closed when writing a card to/reading a
card from disk. Also add a unit test for the error condition when trying
to import a card from a nonexistent file.

virtualsmartcard/src/vpicc/virtualsmartcard/CardGenerator.py

@@ -382,16 +382,19 @@ class CardGenerator(object):
 
     def loadCard(self, filename):
         """Load a card from disk"""
-        db = anydbm.open(filename, 'r')
-
         if self.password is None:
             self.password = getpass.getpass("Please enter your password:")
 
+        db = anydbm.open(filename, 'r')
+        try:
             serializedMF = read_protected_string(db["mf"], self.password)
             serializedSAM = read_protected_string(db["sam"], self.password)
+            self.type = db["type"]
+        finally:
+            db.close()
+
         self.sam = loads(serializedSAM)
         self.mf = loads(serializedMF)
-        self.type = db["type"]
 
     def saveCard(self, filename):
         """Save the currently running card to disk"""
@@ -413,10 +416,12 @@ class CardGenerator(object):
         protectedSAM = protect_string(sam_string, self.password)
 
         db = anydbm.open(filename, 'c')
+        try:
             db["mf"] = protectedMF
             db["sam"] = protectedSAM
             db["type"] = self.type
             db["version"] = "0.1"
+        finally:
             db.close()
 
 if __name__ == "__main__":

virtualsmartcard/src/vpicc/virtualsmartcard/tests/CardGenerator_test.py

@@ -17,9 +17,10 @@
 # virtualsmartcard.  If not, see <http://www.gnu.org/licenses/>.
 #
 
-import unittest
-import tempfile
+import anydbm
 import os
+import tempfile
+import unittest
 from virtualsmartcard.CardGenerator import CardGenerator
 
 class TestNPACardGenerator(unittest.TestCase):
@@ -29,15 +30,13 @@ class TestNPACardGenerator(unittest.TestCase):
         self.nPA_generator = CardGenerator('nPA')
         self.nPA_generator.password = "TestPassword"
 
-    def tearDown(self):
-        os.unlink(self.filename)
-
     def test_nPA_creation(self):
         self.nPA_generator.generateCard()
         self.nPA_generator.saveCard(self.filename)
         mf, sam = self.nPA_generator.getCard()
         self.assertIsNotNone(mf)
         self.assertIsNotNone(sam)
+        os.unlink(self.filename)
 
     def test_load_nPA_from_file_nPA_from_file(self):
         self.nPA_generator.generateCard()
@@ -48,6 +47,11 @@ class TestNPACardGenerator(unittest.TestCase):
         mf, sam = local_generator.getCard()
         self.assertIsNotNone(mf)
         self.assertIsNotNone(sam)
+        os.unlink(self.filename)
+
+    def test_load_nonexistent_file(self):
+        with self.assertRaises(anydbm.error):
+            self.nPA_generator.loadCard(self.filename)
 
 if __name__ == '__main__':
     unittest.main()