Better error reporting if backup file not found

qvm-backup-restore will now show a File Not Found message
if specified backup file is not found.

fixes QubesOS/qubes-issues#3446

qubesadmin/tests/tools/qvm_backup_restore.py

@@ -38,7 +38,9 @@ def tearDown(self):
     @mock.patch('qubesadmin.tools.qvm_backup_restore.input', create=True)
     @mock.patch('getpass.getpass')
     @mock.patch('qubesadmin.tools.qvm_backup_restore.BackupRestore')
-    def test_000_simple(self, mock_backup, mock_getpass, mock_input):
+    @mock.patch('os.path.exists', return_value=True)
+    def test_000_simple(self, _mock_exists,
+                        mock_backup, mock_getpass, mock_input):
         mock_getpass.return_value = 'testpass'
         mock_input.return_value = 'Y'
         vm1 = BackupVM()
@@ -68,7 +70,9 @@ def test_000_simple(self, mock_backup, mock_getpass, mock_input):
     @mock.patch('qubesadmin.tools.qvm_backup_restore.input', create=True)
     @mock.patch('getpass.getpass')
     @mock.patch('qubesadmin.tools.qvm_backup_restore.BackupRestore')
-    def test_001_selected_vms(self, mock_backup, mock_getpass, mock_input):
+    @mock.patch('os.path.exists', return_value=True)
+    def test_001_selected_vms(self, _mock_exist,
+                              mock_backup, mock_getpass, mock_input):
         mock_getpass.return_value = 'testpass'
         mock_input.return_value = 'Y'
         vm1 = BackupVM()
@@ -235,6 +239,14 @@ def test_012_handle_broken_missing_netvm(self):
                     self.app, mock_args, mock_restore_info)
             self.assertAppropriateLogging('NetVM', 'error')
 
+    @mock.patch('argparse.ArgumentParser.error')
+    def test_013_missing_file(self, mock_argparse):
+        mock_argparse.side_effect = qubesadmin.exc.QubesException('Error')
+        with self.assertRaises(qubesadmin.exc.QubesException):
+            qubesadmin.tools.qvm_backup_restore.main(['/some/path'],
+                                                     app=self.app)
+        mock_argparse.assert_called_once_with("File not found: '/some/path'")
+
     def test_100_restore_in_dispvm_parser(self):
         """Verify if qvm-backup-restore tool options matches un-parser
         for paranoid restore mode"""

qubesadmin/tools/qvm_backup_restore.py

@@ -238,6 +238,9 @@ def main(args=None, app=None):
     if args.location_is_service and not args.appvm:
         parser.error('--location-is-service option requires -d')
 
+    if not os.path.exists(args.backup_location):
+        parser.error('File not found: {!r}'.format(args.backup_location))
+
     if args.paranoid_mode:
         args.dom0_home = False
         args.app.log.info("Starting restore process in a DisposableVM...")