Use new-style Python classes

There are some classes in the code that didn't inherited from
nothing and this is an old-style classes. A "New Class" is the
recommended way to create a class in modern Python.A "New Class"
should always inherit from `object` or another new-style class.

Hacking rule added as well.

Change-Id: I2c72f20695e35e05435d2526d4a804196c2ab2d3

tests/hacking/README.rst

@@ -28,6 +28,7 @@ Rally Specific Commandments
 * [N352] - Ensure that string formatting only uses a mapping if multiple mapping keys are used.
 * [N353] - Ensure that unicode() function is not uset because of absence in py3
 * [N354] - Ensure that ``:raises: Exception`` is not used
+* [N355] - Ensure that we use only "new-style" Python classes
 * [N360-N370] - Reserved for rules related to CLI
  * [N360] - Ensure that CLI modules do not use ``rally.common.db``
  * [N361] - Ensure that CLI modules do not use ``rally.common.objects``

tests/hacking/checks.py

@@ -63,6 +63,7 @@ re_raises = re.compile(
     r"\s:raise[^s] *.*$|\s:raises *:.*$|\s:raises *[^:]+$")
 re_db_import = re.compile(r"^from rally.common import db")
 re_objects_import = re.compile(r"^from rally.common import objects")
+re_old_type_class = re.compile(r"^\s*class \w+(\(\))?:")
 
 
 def skip_ignored_lines(func):
@@ -475,6 +476,19 @@ def check_raises(physical_line, filename):
                        "in docstrings.")
 
 
+@skip_ignored_lines
+def check_old_type_class(logical_line, physical_line, filename):
+    """Use new-style Python classes
+
+    N355
+    """
+
+    if re_old_type_class.search(logical_line):
+        yield (0, "N355 This class does not inherit from anything and thus "
+                  "will be an old-style class by default. Try to inherit from "
+                  "``object`` or another new-style class.")
+
+
 @skip_ignored_lines
 def check_db_imports_in_cli(logical_line, physical_line, filename):
     """Ensure that CLI modules do not use ``rally.common.db``
@@ -522,3 +536,4 @@ def factory(register):
     register(check_raises)
     register(check_db_imports_in_cli)
     register(check_objects_imports_in_cli)
+    register(check_old_type_class)

tests/unit/test_hacking.py

@@ -367,3 +367,12 @@ class HackingTestCase(test.TestCase):
         checkres = checks.check_objects_imports_in_cli(
             line, line, "./filename")
         self.assertRaises(StopIteration, next, checkres)
+
+    @ddt.data(
+        "class Oldstype():",
+        "class Oldstyle:"
+    )
+    def test_check_old_type_class(self, line):
+        checkres = checks.check_old_type_class(line, line, "fakefile")
+        self.assertIsNotNone(next(checkres))
+        self.assertEqual([], list(checkres))