[ci] Get back testing samples

Change-Id: I7b4777fa502f2b9da5770d67947357a02b5f1ad0

.zuul.d/python-jobs.yaml

@@ -87,6 +87,16 @@
     vars:
       tox_env: py38
 
+- job:
+    name: rally-tox-samples
+    parent: rally-tox-base
+    description: |
+      Run unit test for rally project.
+
+      Uses tox with the ``samples`` environment.
+    vars:
+      tox_env: samples
+
 - job:
     name: rally-tox-cover
     parent: tox-cover

.zuul.d/zuul.yaml

@@ -88,6 +88,7 @@
         - rally-tox-py36
         - rally-tox-py37
         - rally-tox-py38
+        - rally-tox-samples
         - rally-tox-functional
         - rally-tox-functional-py38
         - rally-tox-self

tests/samples/test_task_samples.py

@@ -17,8 +17,8 @@ import inspect
 import itertools
 import os
 import traceback
+from unittest import mock
 
-import mock
 import yaml
 
 import rally
@@ -37,10 +37,7 @@ class TaskSampleTestCase(test.TestCase):
 
     def setUp(self):
         super(TaskSampleTestCase, self).setUp()
-        if os.environ.get("TOX_ENV_NAME") == "cover":
-            self.skipTest("There is no need to check samples in coverage job.")
-        with mock.patch("rally.api.API.check_db_revision"):
-            self.rapi = api.API()
+        self.rapi = api.API(skip_db_check=True)
 
     def iterate_samples(self, merge_pairs=True):
         """Iterates all task samples

tox.ini

@@ -40,6 +40,12 @@ basepython = python3.7
 [testenv:py38]
 basepython = python3.8
 
+[testenv:samples]
+commands =
+  find . -type f -name "*.pyc" -delete
+  python {toxinidir}/tests/ci/pytest_launcher.py tests/samples --posargs={posargs}
+
+
 [testenv:venv]
 commands = {posargs}