Return nothing from Put Cache Entry in CMC

[alex-chew]

See awslabs/aws-encryption-sdk-specification#194.

Current implementation:

aws-encryption-sdk-python/src/aws_encryption_sdk/caches/base.py

Lines 26 to 47 in c961999

	@abc.abstractmethod
	def put_encryption_materials(self, cache_key, encryption_materials, plaintext_length, entry_hints=None):
	"""Adds encryption materials to the cache.
	:param bytes cache_key: Identifier for entries in cache
	:param encryption_materials: Encryption materials to add to cache
	:type encryption_materials: aws_encryption_sdk.materials_managers.EncryptionMaterials
	:param int plaintext_length: Length of plaintext associated with this request to the cache
	:param entry_hints: Metadata to associate with entry (optional)
	:type entry_hints: aws_encryption_sdk.caches.CryptoCacheEntryHints
	:rtype: aws_encryption_sdk.caches.CryptoCacheEntry
	"""
	@abc.abstractmethod
	def put_decryption_materials(self, cache_key, decryption_materials):
	"""Adds decryption materials to the cache
	:param bytes cache_key: Identifier for entries in cache
	:param decryption_materials: Decryption materials to add to cache
	:type decryption_materials: aws_encryption_sdk.materials_managers.DecryptionMaterials
	:rtype: aws_encryption_sdk.caches.CryptoCacheEntry
	"""

[farleyb-amazon]

We have longer term plans to rework our cache APIs. Resolving.