chore: drop six (#255)

Also, avoid using default environment credentials in unit tests

google/cloud/automl_v1beta1/services/tables/tables_client.py

@@ -19,7 +19,6 @@
 import copy
 import logging
 import pkg_resources
-import six
 
 from google.api_core.gapic_v1 import client_info
 
@@ -63,9 +62,9 @@ def to_proto_value(value):
         # This check needs to happen before isinstance(value, int),
         # isinstance(value, int) returns True when value is bool.
         return struct_pb2.Value(bool_value=value), None
-    elif isinstance(value, six.integer_types) or isinstance(value, float):
+    elif isinstance(value, int) or isinstance(value, float):
         return struct_pb2.Value(number_value=value), None
-    elif isinstance(value, six.string_types) or isinstance(value, six.text_type):
+    elif isinstance(value, str):
         return struct_pb2.Value(string_value=value), None
     elif isinstance(value, dict):
         struct_value = struct_pb2.Struct()

tests/unit/test_tables_client_v1beta1.py

@@ -1714,12 +1714,15 @@ def test_prediction_client_credentials(self):
         assert prediction_client_kwargs["credentials"] == credentials_mock
 
     def test_prediction_client_client_info(self):
+        credentials_mock = mock.Mock()
         client_info_mock = mock.Mock()
         patch_prediction_client = mock.patch(
             "google.cloud.automl_v1beta1.services.tables.tables_client.PredictionServiceClient"
         )
         with patch_prediction_client as MockPredictionClient:
-            automl_v1beta1.TablesClient(client_info=client_info_mock)
+            automl_v1beta1.TablesClient(
+                credentials=credentials_mock, client_info=client_info_mock,
+            )
         _, prediction_client_kwargs = MockPredictionClient.call_args
         assert "client_info" in prediction_client_kwargs
         assert prediction_client_kwargs["client_info"] == client_info_mock