Bump bandit version

This patch bumps bandit allowed version to >=1.6.0,<1.7.0 in order to
avoid the errors detailed here https://github.com/PyCQA/bandit/pull/393



Change-Id: I005962a63341bb8585141dfe5dcff3ea79560b87
Signed-off-by: Moisés Guimarães de Medeiros <moguimar@redhat.com>

oslo_versionedobjects/tests/test_exception.py

@@ -40,7 +40,7 @@ class ExceptionTestCase(test.TestCase):
         notifier.reset_mock()
 
         # wrap_exception() must reraise the exception
-        self.assertRaises(ValueError,
+        self.assertRaises(ValueError,  # nosec
                           test.raise_exc, context, exc, admin_password="xxx")
 
         # wrap_exception() strips admin_password from args

test-requirements.txt

@@ -11,4 +11,4 @@ stestr>=2.0.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 
 # Bandit security code scanner
-bandit>=1.1.0,<1.6.0 # Apache-2.0
+bandit>=1.6.0,<1.7.0 # Apache-2.0