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, 3 insertions, 3 deletions

diff --git a/tests/unittests/test_datasource/test_azure_helper.py b/tests/unittests/test_datasource/test_azure_helper.py
index 007df09f..6344b0bb 100644
--- a/tests/unittests/test_datasource/test_azure_helper.py
+++ b/tests/unittests/test_datasource/test_azure_helper.py
@@ -1,7 +1,7 @@
 # This file is part of cloud-init. See LICENSE file for license information.
 
 import os
-import unittest2
+import unittest
 from textwrap import dedent
 
 from cloudinit.sources.helpers import azure as azure_helper
@@ -332,7 +332,7 @@ class TestOpenSSLManagerActions(CiTestCase):
         path = 'tests/data/azure'
         return os.path.join(path, name)
 
-    @unittest2.skip("todo move to cloud_test")
+    @unittest.skip("todo move to cloud_test")
     def test_pubkey_extract(self):
         cert = load_file(self._data_file('pubkey_extract_cert'))
         good_key = load_file(self._data_file('pubkey_extract_ssh_key'))
@@ -344,7 +344,7 @@ class TestOpenSSLManagerActions(CiTestCase):
         fingerprint = sslmgr._get_fingerprint_from_cert(cert)
         self.assertEqual(good_fingerprint, fingerprint)
 
-    @unittest2.skip("todo move to cloud_test")
+    @unittest.skip("todo move to cloud_test")
     @mock.patch.object(azure_helper.OpenSSLManager, '_decrypt_certs_from_xml')
     def test_parse_certificates(self, mock_decrypt_certs):
         """Azure control plane puts private keys as well as certificates