Migrate "test/unit/test_providers_kms_master_key_provider.py" from unittest to pytest (#122)

* Migrating unit/test_deserialize.py from unittest from pytest

* Migrate unit/test_provides_kms_master_key.py from unittest to pytest

* Migrated unit/test/_providers_kms_master_key_provider.py from unittest to pytest

* Removed unit tests not corresponding to this branch

* Added yield and tearDown to apply_fixtures function

* Removed unused import

Author: ansanper

test/unit/test_providers_kms_master_key_provider.py

@@ -11,11 +11,8 @@
 # ANY KIND, either express or implied. See the License for the specific
 # language governing permissions and limitations under the License.
 """Unit test suite from aws_encryption_sdk.key_providers.kms.KMSMasterKeyProvider"""
-import unittest
-
 import botocore.client
 import pytest
-import six
 from mock import ANY, MagicMock, call, patch, sentinel
 
 from aws_encryption_sdk.exceptions import UnknownRegionError
@@ -32,8 +29,9 @@ def test_init_with_regionless_key_ids_and_region_names():
     assert provider.master_key("alias/key_1").config.client.meta.region_name == region_names[0]
 
 
-class TestKMSMasterKeyProvider(unittest.TestCase):
-    def setUp(self):
+class TestKMSMasterKeyProvider(object):
+    @pytest.fixture(autouse=True)
+    def apply_fixtures(self):
         self.mock_botocore_session_patcher = patch("aws_encryption_sdk.key_providers.kms.botocore.session.Session")
         self.mock_botocore_session = self.mock_botocore_session_patcher.start()
         self.mock_boto3_session_patcher = patch("aws_encryption_sdk.key_providers.kms.boto3.session.Session")
@@ -43,8 +41,8 @@ def setUp(self):
         self.mock_boto3_client_instance = MagicMock()
         self.mock_boto3_client_instance.__class__ = botocore.client.BaseClient
         self.mock_boto3_session_instance.client.return_value = self.mock_boto3_client_instance
-
-    def tearDown(self):
+        yield
+        # Run tearDown
         self.mock_botocore_session_patcher.stop()
         self.mock_boto3_session_patcher.stop()
 
@@ -130,10 +128,9 @@ def test_client_no_region_name_with_default(self, mock_add_client):
 
     def test_client_no_region_name_without_default(self):
         test = KMSMasterKeyProvider()
-        with six.assertRaisesRegex(
-            self, UnknownRegionError, "No default region found and no region determinable from key id: *"
-        ):
+        with pytest.raises(UnknownRegionError) as excinfo:
             test._client("")
+        excinfo.match("No default region found and no region determinable from key id: *")
 
     @patch("aws_encryption_sdk.key_providers.kms.KMSMasterKeyProvider._client")
     def test_new_master_key(self, mock_client):