diff --git a/codebuild/py38/awses_local.yml b/codebuild/py38/awses_local.yml
index fe84d714d..b221abe72 100644
--- a/codebuild/py38/awses_local.yml
+++ b/codebuild/py38/awses_local.yml
@@ -20,6 +20,8 @@ phases:
       python: latest
   build:
     commands:
-      - pip install tox
+      - pyenv install 3.8.6
+      - pyenv local 3.8.6
+      - pip install tox tox-pyenv
       - cd test_vector_handlers
       - tox
diff --git a/codebuild/py38/examples.yml b/codebuild/py38/examples.yml
index 180c606f4..c9a9f9a7a 100644
--- a/codebuild/py38/examples.yml
+++ b/codebuild/py38/examples.yml
@@ -18,5 +18,7 @@ phases:
       python: latest
   build:
     commands:
-      - pip install tox
+      - pyenv install 3.8.6
+      - pyenv local 3.8.6
+      - pip install tox tox-pyenv
       - tox
diff --git a/codebuild/py38/integ.yml b/codebuild/py38/integ.yml
index 6af55e839..31cbb7d43 100644
--- a/codebuild/py38/integ.yml
+++ b/codebuild/py38/integ.yml
@@ -18,5 +18,7 @@ phases:
       python: latest
   build:
     commands:
-      - pip install tox
+      - pyenv install 3.8.6
+      - pyenv local 3.8.6
+      - pip install tox tox-pyenv
       - tox
diff --git a/decrypt_oracle/setup.py b/decrypt_oracle/setup.py
index 72c56dd04..c56d64911 100644
--- a/decrypt_oracle/setup.py
+++ b/decrypt_oracle/setup.py
@@ -10,7 +10,7 @@
 
 def read(*args):
     """Read complete file contents."""
-    return open(os.path.join(HERE, *args)).read()  # pylint: disable=consider-using-with
+    return open(os.path.join(HERE, *args), encoding="utf-8").read()  # pylint: disable=consider-using-with
 
 
 def get_version():
diff --git a/decrypt_oracle/test/integration/integration_test_utils.py b/decrypt_oracle/test/integration/integration_test_utils.py
index eeb6219ac..c03b7f440 100644
--- a/decrypt_oracle/test/integration/integration_test_utils.py
+++ b/decrypt_oracle/test/integration/integration_test_utils.py
@@ -100,7 +100,7 @@ def test_vectors_filename() -> Text:
 def all_test_vectors() -> Iterable[Any]:
     """Collect and iterate through all test vectors."""
 
-    with open(test_vectors_filename(), "r") as vectors_file:
+    with open(test_vectors_filename(), "r", encoding="utf-8") as vectors_file:
         raw_vectors = json.load(vectors_file)
 
     for vector in raw_vectors:
diff --git a/examples/src/one_kms_cmk_streaming_data.py b/examples/src/one_kms_cmk_streaming_data.py
index 88eb4eb5c..f4e5ce476 100644
--- a/examples/src/one_kms_cmk_streaming_data.py
+++ b/examples/src/one_kms_cmk_streaming_data.py
@@ -25,7 +25,7 @@ def encrypt_decrypt_stream(key_arn, source_plaintext_filename, botocore_session=
     :param botocore_session: existing botocore session instance
     :type botocore_session: botocore.session.Session
     """
-    kwargs = dict()
+    kwargs = {}
 
     kwargs["key_ids"] = [key_arn]
 
diff --git a/setup.py b/setup.py
index a755b75ad..bfe48b091 100644
--- a/setup.py
+++ b/setup.py
@@ -10,7 +10,7 @@
 
 def read(*args):
     """Reads complete file contents."""
-    return open(os.path.join(HERE, *args)).read()  # pylint: disable=consider-using-with
+    return open(os.path.join(HERE, *args), encoding="utf-8").read()  # pylint: disable=consider-using-with
 
 
 def get_version():
diff --git a/src/aws_encryption_sdk/internal/formatting/deserialize.py b/src/aws_encryption_sdk/internal/formatting/deserialize.py
index d2cfb1095..b06b5ba11 100644
--- a/src/aws_encryption_sdk/internal/formatting/deserialize.py
+++ b/src/aws_encryption_sdk/internal/formatting/deserialize.py
@@ -344,7 +344,7 @@ def deserialize_header(stream, max_encrypted_data_keys=None):
     tee_stream = TeeStream(stream, tee)
     (version_id,) = unpack_values(">B", tee_stream)
     version = _verified_version_from_id(version_id)
-    header = dict()
+    header = {}
     header["version"] = version
 
     if version == SerializationVersion.V1:
diff --git a/test/functional/test_f_xcompat.py b/test/functional/test_f_xcompat.py
index e87082503..790724367 100644
--- a/test/functional/test_f_xcompat.py
+++ b/test/functional/test_f_xcompat.py
@@ -126,7 +126,7 @@ def _generate_test_cases():  # noqa=C901
         # Make no test cases if the ciphertext file is not found
         return []
 
-    with open(ciphertext_manifest_path) as f:
+    with open(ciphertext_manifest_path, encoding="utf-8") as f:
         ciphertext_manifest = json.load(f)
     _test_cases = []
 
diff --git a/test/integration/test_i_xcompat_kms.py b/test/integration/test_i_xcompat_kms.py
index b6f22a3ff..7cfeee111 100644
--- a/test/integration/test_i_xcompat_kms.py
+++ b/test/integration/test_i_xcompat_kms.py
@@ -48,7 +48,7 @@ def _generate_test_cases():
         # Make no test cases if the ciphertext file is not found
         return []
 
-    with open(ciphertext_manifest_path) as f:
+    with open(ciphertext_manifest_path, encoding="utf-8") as f:
         ciphertext_manifest = json.load(f)
     _test_cases = []
 
@@ -69,9 +69,9 @@ def _generate_test_cases():
 @pytest.mark.parametrize("plaintext_filename, ciphertext_filename", _generate_test_cases())
 def test_decrypt_from_file(plaintext_filename, ciphertext_filename):
     """Tests decrypt from known good files."""
-    with open(ciphertext_filename, "rb") as infile:
+    with open(ciphertext_filename, "rb", encoding="utf-8") as infile:
         ciphertext = infile.read()
-    with open(plaintext_filename, "rb") as infile:
+    with open(plaintext_filename, "rb", encoding="utf-8") as infile:
         plaintext = infile.read()
     decrypted_ciphertext, _header = aws_encryption_sdk.decrypt(
         source=ciphertext, key_provider=setup_kms_master_key_provider()
diff --git a/test/integration/test_kat_commitment.py b/test/integration/test_kat_commitment.py
index fa97600f0..e72277787 100644
--- a/test/integration/test_kat_commitment.py
+++ b/test/integration/test_kat_commitment.py
@@ -50,7 +50,7 @@ def _file_root():
 base_dir = os.path.join(root_dir, "test", "resources")
 file_path = os.path.join(base_dir, FILE_NAME)
 
-test_str = open(file_path, "r").read()  # pylint: disable=consider-using-with
+test_str = open(file_path, "r", encoding="utf-8").read()  # pylint: disable=consider-using-with
 test_json = json.loads(test_str)
 kat_tests = test_json["tests"]
 
diff --git a/test/unit/test_encryption_client.py b/test/unit/test_encryption_client.py
index f463b04f1..db2ca1c4c 100644
--- a/test/unit/test_encryption_client.py
+++ b/test/unit/test_encryption_client.py
@@ -59,7 +59,7 @@ def test_client_encrypt(mocker):
         commitment_policy=CommitmentPolicy.FORBID_ENCRYPT_ALLOW_DECRYPT, max_encrypted_data_keys=3
     )
 
-    kwargs = dict()
+    kwargs = {}
     kwargs["source"] = b"plaintext"
     kwargs["materials_manager"] = cmm
     client.encrypt(**kwargs)
@@ -77,7 +77,7 @@ def test_client_decrypt(mocker):
         commitment_policy=CommitmentPolicy.FORBID_ENCRYPT_ALLOW_DECRYPT, max_encrypted_data_keys=3
     )
 
-    kwargs = dict()
+    kwargs = {}
     kwargs["source"] = b"ciphertext"
     kwargs["materials_manager"] = cmm
     client.decrypt(**kwargs)
@@ -94,7 +94,7 @@ def test_client_stream_encrypt(mocker, mode_string):
     cmm = MagicMock(__class__=CryptoMaterialsManager)
     client = aws_encryption_sdk.EncryptionSDKClient(commitment_policy=CommitmentPolicy.FORBID_ENCRYPT_ALLOW_DECRYPT)
 
-    kwargs = dict()
+    kwargs = {}
     kwargs["mode"] = mode_string
     kwargs["source"] = b"plaintext"
     kwargs["materials_manager"] = cmm
@@ -113,7 +113,7 @@ def test_client_stream_decrypt(mocker, mode_string):
     cmm = MagicMock(__class__=CryptoMaterialsManager)
     client = aws_encryption_sdk.EncryptionSDKClient(commitment_policy=CommitmentPolicy.FORBID_ENCRYPT_ALLOW_DECRYPT)
 
-    kwargs = dict()
+    kwargs = {}
     kwargs["mode"] = mode_string
     kwargs["source"] = b"ciphertext"
     kwargs["materials_manager"] = cmm
@@ -132,7 +132,7 @@ def test_client_bad_kwargs(mocker, method, key):
     mocker.patch.object(aws_encryption_sdk, "StreamEncryptor")
 
     cmm = MagicMock(__class__=CryptoMaterialsManager)
-    kwargs = dict()
+    kwargs = {}
     kwargs[key] = "foobar"
     kwargs["source"] = b"ciphertext"
     kwargs["materials_manager"] = cmm
diff --git a/test/unit/test_material_managers.py b/test/unit/test_material_managers.py
index 22a7a753e..2d892bd36 100644
--- a/test/unit/test_material_managers.py
+++ b/test/unit/test_material_managers.py
@@ -68,7 +68,7 @@
         (EncryptionMaterials, dict(data_encryption_key=None)),
         (EncryptionMaterials, dict(encrypted_data_keys=None)),
         (EncryptionMaterials, dict(encryption_context=None)),
-        (EncryptionMaterials, dict(signing_key=u"not bytes or None")),
+        (EncryptionMaterials, dict(signing_key="not bytes or None")),
         (DecryptionMaterialsRequest, dict(algorithm=None)),
         (DecryptionMaterialsRequest, dict(encrypted_data_keys=None)),
         (DecryptionMaterialsRequest, dict(encryption_context=None)),
diff --git a/test/unit/test_util_str_ops.py b/test/unit/test_util_str_ops.py
index 1778bc4a0..5a6ef2546 100644
--- a/test/unit/test_util_str_ops.py
+++ b/test/unit/test_util_str_ops.py
@@ -39,17 +39,17 @@ def test_to_bytes_bytes2bytes(self):
         assert test == b"\x3a\x00\x99"
 
     def test_to_str_bytes2unicode(self):
-        test = aws_encryption_sdk.internal.str_ops.to_str(codecs.encode(u"Предисловие", "utf-8"))
-        assert test == u"Предисловие"
+        test = aws_encryption_sdk.internal.str_ops.to_str(codecs.encode("Предисловие", "utf-8"))
+        assert test == "Предисловие"
 
     def test_to_str_unicode2unicode(self):
-        test = aws_encryption_sdk.internal.str_ops.to_str(u"Предисловие")
-        assert test == u"Предисловие"
+        test = aws_encryption_sdk.internal.str_ops.to_str("Предисловие")
+        assert test == "Предисловие"
 
     def test_to_str_unicode2bytes(self):
-        test = aws_encryption_sdk.internal.str_ops.to_bytes(u"Предисловие")
-        assert test == codecs.encode(u"Предисловие", "utf-8")
+        test = aws_encryption_sdk.internal.str_ops.to_bytes("Предисловие")
+        assert test == codecs.encode("Предисловие", "utf-8")
 
     def test_to_bytes_utf82utf8(self):
-        test = aws_encryption_sdk.internal.str_ops.to_bytes(codecs.encode(u"Предисловие", "utf-8"))
-        assert test == codecs.encode(u"Предисловие", "utf-8")
+        test = aws_encryption_sdk.internal.str_ops.to_bytes(codecs.encode("Предисловие", "utf-8"))
+        assert test == codecs.encode("Предисловие", "utf-8")
diff --git a/test/unit/test_utils.py b/test/unit/test_utils.py
index 72f98e731..c6d565108 100644
--- a/test/unit/test_utils.py
+++ b/test/unit/test_utils.py
@@ -35,7 +35,7 @@ def test_prep_stream_data_passthrough():
     assert_prepped_stream_identity(test, io.BytesIO)
 
 
-@pytest.mark.parametrize("source", (u"some unicode data ловие", b"\x00\x01\x02"))
+@pytest.mark.parametrize("source", ("some unicode data ловие", b"\x00\x01\x02"))
 def test_prep_stream_data_wrap(source):
     test = aws_encryption_sdk.internal.utils.prep_stream_data(source)
 
diff --git a/test_vector_handlers/setup.py b/test_vector_handlers/setup.py
index 661ea722c..9a89fb698 100644
--- a/test_vector_handlers/setup.py
+++ b/test_vector_handlers/setup.py
@@ -10,7 +10,7 @@
 
 def read(*args):
     """Read complete file contents."""
-    return open(os.path.join(HERE, *args)).read()  # pylint: disable=consider-using-with
+    return open(os.path.join(HERE, *args), encoding="utf-8").read()  # pylint: disable=consider-using-with
 
 
 def get_version():