hanging object references in helper functions avoided

[abdulsmapara]

resolves: #44

Description of changes:

• Avoided hanging object references in helper functions -
  • Created a deep copy of header and keyring trace objects from the managed stream before passing them to CryptoResult in the encrypt[1] and decrypt[2] functions.
  • Modified the test for checking equality of header but not identity

[1]

aws-encryption-sdk-python/src/aws_encryption_sdk/__init__.py

Lines 84 to 87 in 82e2156

	with StreamEncryptor(**kwargs) as encryptor:
	ciphertext = encryptor.read()
	return CryptoResult(result=ciphertext, header=encryptor.header, keyring_trace=encryptor.keyring_trace)

[2]

aws-encryption-sdk-python/src/aws_encryption_sdk/__init__.py

Lines 143 to 146 in 82e2156

	with StreamDecryptor(**kwargs) as decryptor:
	plaintext = decryptor.read()
	return CryptoResult(result=plaintext, header=decryptor.header, keyring_trace=decryptor.keyring_trace)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[mattsb42-aws]

Thanks for the contribution!
It looks like there are a bunch of tests where we currently check identity (ex: assert header is expected_header) that will need to be changed to check the new requirement: equality but NOT identity (ex:

assert header == expected_header
assert header is not expected_header

Also, please run tox -e autoformat to take care of the formatting issues that our CI is blocking on.

[abdulsmapara]

@mattsb42-aws, added commits as per the comments.

[mattsb42-aws]

Looks good! Thanks for the contribution. :)