Add load_test mechanism for InputScenarioUtils

Similar to what was done for the negative test framework this commit
adds a method to handle using CONF values with testscenarios.
Previously the attr's were set in the test class definition which
would force a getattr at import time. This will cause issues if the
config file is not present. By adding a method which won't be executed
at import but rather when the tests are run we can avoid this.

Change-Id: Ib635f8b895f6642f78a3af644170700f72259d46

tempest/scenario/test_server_basic_ops.py

@@ -20,13 +20,11 @@ from tempest.scenario import manager
 from tempest.scenario import utils as test_utils
 from tempest import test
 
-import testscenarios
-
 CONF = config.CONF
 
 LOG = logging.getLogger(__name__)
 
-load_tests = testscenarios.load_tests_apply_scenarios
+load_tests = test_utils.load_tests_input_scenario_utils
 
 
 class TestServerBasicOps(manager.OfficialClientTest):
@@ -43,13 +41,6 @@ class TestServerBasicOps(manager.OfficialClientTest):
      * Terminate the instance
     """
 
-    scenario_utils = test_utils.InputScenarioUtils()
-    scenario_flavor = scenario_utils.scenario_flavors
-    scenario_image = scenario_utils.scenario_images
-
-    scenarios = testscenarios.multiply_scenarios(scenario_image,
-                                                 scenario_flavor)
-
     def setUp(self):
         super(TestServerBasicOps, self).setUp()
         # Setup image and flavor the test instance

tempest/scenario/utils.py

@@ -12,6 +12,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import testscenarios
+import testtools
+
 from tempest import clients
 from tempest.common.utils import misc
 from tempest import config
@@ -134,3 +137,22 @@ class InputScenarioUtils(object):
                 for f in flavors if re.search(self.flavor_pattern, str(f.name))
             ]
         return self._scenario_flavors
+
+
+def load_tests_input_scenario_utils(*args):
+    """
+    Wrapper for testscenarios to set the scenarios to avoid running a getattr
+    on the CONF object at import.
+    """
+    if getattr(args[0], 'suiteClass', None) is not None:
+        loader, standard_tests, pattern = args
+    else:
+        standard_tests, module, loader = args
+    scenario_utils = InputScenarioUtils()
+    scenario_flavor = scenario_utils.scenario_flavors
+    scenario_image = scenario_utils.scenario_images
+    for test in testtools.iterate_tests(standard_tests):
+        setattr(test, 'scenarios', testscenarios.multiply_scenarios(
+            scenario_image,
+            scenario_flavor))
+    return testscenarios.load_tests_apply_scenarios(*args)