More compatibility with Python 3

- use the six version of configparser and urllib, and depends on six;
- remove relative imports;
- adapt few tests to the changes.

The changes above should be noop from the point of view of
functionalities, at least on python 2.

And also:
- replace the py34 tox virtualenv with py35;
- add a non-voting py35 job (locally for now, it will be enabled
  to project-config also for gating when stable).

Story: 2002574
Task: 22142
Change-Id: I0a35abaae6f5b7095ebae765fbe2163046e0a4da

config_tempest/tests/services/test_ceilometer.py

@@ -13,7 +13,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import ConfigParser
+
+from six.moves import configparser
 
 from config_tempest.services import ceilometer
 from config_tempest.tempest_conf import TempestConf
@@ -29,7 +30,7 @@ class TestCeilometerService(BaseServiceTest):
         client_service_mock = self.FakeServiceClient(services={})
         ceilometer.check_ceilometer_service(self.conf, client_service_mock)
 
-        self._assert_conf_get_not_raises(ConfigParser.NoSectionError,
+        self._assert_conf_get_not_raises(configparser.NoSectionError,
                                          "service_available",
                                          "ceilometer")
 

config_tempest/tests/services/test_horizon.py

@@ -28,7 +28,8 @@ class TestConfigTempest(BaseConfigTempestTest):
 
     def test_configure_horizon_ipv4(self):
         mock_function = mock.Mock(return_value=True)
-        self.useFixture(MonkeyPatch('urllib2.urlopen', mock_function))
+        self.useFixture(MonkeyPatch('six.moves.urllib.request.urlopen',
+                                    mock_function))
         horizon.configure_horizon(self.conf)
         self.assertEqual(self.conf.get('service_available', 'horizon'), "True")
         self.assertEqual(self.conf.get('dashboard', 'dashboard_url'),
@@ -38,7 +39,8 @@ class TestConfigTempest(BaseConfigTempestTest):
 
     def test_configure_horizon_ipv6(self):
         mock_function = mock.Mock(return_value=True)
-        self.useFixture(MonkeyPatch('urllib2.urlopen', mock_function))
+        self.useFixture(MonkeyPatch('six.moves.urllib.request.urlopen',
+                                    mock_function))
         self.conf.set('identity', 'uri', 'http://[::1]:5000/v3', priority=True)
         horizon.configure_horizon(self.conf)
         self.assertEqual(self.conf.get('service_available', 'horizon'), "True")