Migrate "test/unit/test_providers_raw_master_key_provider.py" from unittest to pytest (#124)

* 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

* unit/test_providers_raw_master_key.py

* Migrate unit/test_providers_raw_master_key_provider.py from unittest from pytest

* Removed unit tests not corresponding to this branch

* Removed unused import

Author: ansanper

test/unit/test_providers_raw_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.
 """Test suite for aws_encryption_sdk.key_providers.raw.RawMasterKeyProvider"""
-import unittest
-
 import attr
 import pytest
-import six
 from mock import MagicMock, patch, sentinel
 
 from aws_encryption_sdk.key_providers.base import MasterKeyProvider, MasterKeyProviderConfig
@@ -42,16 +39,17 @@ def _get_raw_key(self, key_id):
         return self.config.mock_wrapping_key
 
 
-class TestRawMasterKeyProvider(unittest.TestCase):
+class TestRawMasterKeyProvider(object):
     def test_parent(self):
         assert issubclass(RawMasterKeyProvider, MasterKeyProvider)
 
     def test_get_raw_key_enforcement(self):
         class TestProvider(RawMasterKeyProvider):
             pass
 
-        with six.assertRaisesRegex(self, TypeError, "Can't instantiate abstract class TestProvider *"):
+        with pytest.raises(TypeError) as excinfo:
             TestProvider()
+        excinfo.match("Can't instantiate abstract class TestProvider *")
 
     @patch(
         "aws_encryption_sdk.key_providers.raw.RawMasterKeyConfig", return_value=sentinel.raw_master_key_config_instance