cloudinit: drop dependencies on unittest2 and contextlib2 (#322)

These libraries provide backports of Python 3's stdlib components to Python 2. As we only support Python 3, we can simply use the stdlib now. This pull request does the following:

* removes some unneeded compatibility code for the old spelling of `assertRaisesRegex`
* replaces invocations of the Python 2-only `assertItemsEqual` with its new name, `assertCountEqual`
* replaces all usage of `unittest2` with `unittest`
* replaces all usage of `contextlib2` with `contextlib`
* drops `unittest2` and `contextlib2` from requirements files and tox.ini

It also rewrites some `test_azure` helpers to use bare asserts. We were seeing a strange error in xenial builds of this branch which appear to be stemming from the AssertionError that pytest produces being _different_ from the standard AssertionError.  This means that the modified helpers weren't behaving correctly, because they weren't catching AssertionErrors as one would expect. (I believe this is related, in some way, to https://github.com/pytest-dev/pytest/issues/645, but the only version of pytest where we're affected is so far in the past that it's not worth pursuing it any further as we have a workaround.)

1 files changed, 7 insertions, 21 deletions

diff --git a/cloudinit/tests/helpers.py b/cloudinit/tests/helpers.py
index f4db5827..477e14c2 100644
--- a/cloudinit/tests/helpers.py
+++ b/cloudinit/tests/helpers.py
@@ -13,15 +13,10 @@ import string
 import sys
 import tempfile
 import time
+import unittest
+from contextlib import ExitStack, contextmanager
 from unittest import mock
-
-import unittest2
-from unittest2.util import strclass
-
-try:
-    from contextlib import ExitStack, contextmanager
-except ImportError:
-    from contextlib2 import ExitStack, contextmanager
+from unittest.util import strclass
 
 from cloudinit.config.schema import (
     SchemaValidationError, validate_cloudconfig_schema)
@@ -35,8 +30,8 @@ from cloudinit import util
 _real_subp = util.subp
 
 # Used for skipping tests
-SkipTest = unittest2.SkipTest
-skipIf = unittest2.skipIf
+SkipTest = unittest.SkipTest
+skipIf = unittest.skipIf
 
 
 # Makes the old path start
@@ -73,7 +68,7 @@ def retarget_many_wrapper(new_base, am, old_func):
     return wrapper
 
 
-class TestCase(unittest2.TestCase):
+class TestCase(unittest.TestCase):
 
     def reset_global_state(self):
         """Reset any global state to its original settings.
@@ -372,7 +367,7 @@ class HttprettyTestCase(CiTestCase):
         super(HttprettyTestCase, self).tearDown()
 
 
-class SchemaTestCaseMixin(unittest2.TestCase):
+class SchemaTestCaseMixin(unittest.TestCase):
 
     def assertSchemaValid(self, cfg, msg="Valid Schema failed validation."):
         """Assert the config is valid per self.schema.
@@ -504,13 +499,4 @@ if not hasattr(mock.Mock, 'assert_not_called'):
             raise AssertionError(msg)
     mock.Mock.assert_not_called = __mock_assert_not_called
 
-
-# older unittest2.TestCase (centos6) have only the now-deprecated
-# assertRaisesRegexp. Simple assignment makes pylint complain, about
-# users of assertRaisesRegex so we use getattr to trick it.
-# https://github.com/PyCQA/pylint/issues/1946
-if not hasattr(unittest2.TestCase, 'assertRaisesRegex'):
-    unittest2.TestCase.assertRaisesRegex = (
-        getattr(unittest2.TestCase, 'assertRaisesRegexp'))
-
 # vi: ts=4 expandtab