Fix flake8 failures

Author: farleyb-amazon

test_vector_handlers/src/awses_test_vectors/manifests/full_message/decrypt.py

@@ -91,6 +91,7 @@ def __init__(
         description=None,  # type: Optional[str]
     ):  # noqa=D107
         # type: (...) -> None
+        """Set initial values for the test scenario."""
         # Workaround pending resolution of attrs/mypy interaction.
         # https://github.com/python/mypy/issues/2088
         # https://github.com/python-attrs/attrs/issues/215
@@ -200,6 +201,7 @@ def __init__(
         client_version=aws_encryption_sdk.__version__,  # type: Optional[str]
     ):  # noqa=D107
         # type: (...) -> None
+        """Set initial values for the manifest."""
         # Workaround pending resolution of attrs/mypy interaction.
         # https://github.com/python/mypy/issues/2088
         # https://github.com/python-attrs/attrs/issues/215

test_vector_handlers/src/awses_test_vectors/manifests/keys.py

@@ -142,6 +142,7 @@ def __init__(
         material,  # type: Iterable[str]
     ):  # noqa=D107
         # type: (...) -> None
+        """Set initial values for the ManualKeySpec."""
         # Workaround pending resolution of attrs/mypy interaction.
         # https://github.com/python/mypy/issues/2088
         # https://github.com/python-attrs/attrs/issues/215