chore: checkout corresponding branch instead of commit

Author: josecorella

codebuild/release/prod-release.yml

@@ -2,7 +2,7 @@ version: 0.2
 
 env:
   variables:
-    BRANCH: "master"
+    BRANCH: "mainline-1.x"
   secrets-manager:
     TWINE_USERNAME: PyPiAdmin:username 
     TWINE_PASSWORD: PyPiAdmin:password

codebuild/release/test-release.yml

@@ -2,7 +2,7 @@ version: 0.2
 
 env:
   variables:
-    BRANCH: "master"
+    BRANCH: "mainline-1.x"
   secrets-manager:
     TWINE_USERNAME: TestPyPiCryptoTools:username 
     TWINE_PASSWORD: TestPyPiCryptoTools:password

test/functional/test_f_aws_encryption_sdk_client.py

@@ -15,6 +15,7 @@
 
 import io
 import logging
+from distutils.version import StrictVersion
 
 import attr
 import botocore.client
@@ -23,7 +24,6 @@
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric import padding
-from distutils.version import StrictVersion
 from mock import MagicMock
 from wrapt import ObjectProxy