optimize response validation: if validation failed, then raise ValidationError directly

ate/task.py

@@ -14,8 +14,7 @@ class ApiTestCase(unittest.TestCase):
     def runTest(self):
         """ run testcase and check result.
         """
-        result = self.test_runner.run_test(self.testcase)
-        self.assertEqual(result, (True, []))
+        self.assertTrue(self.test_runner.run_test(self.testcase))
 
 def create_suite(testset):
     """ create test suite with a testset, it may include one or several testcases.