Lint fix.

Author: IlyaFaer

api_core/noxfile.py

@@ -63,7 +63,7 @@ def unit_grpc_gcp(session):
     default(session)
 
 
-@nox.session(python="3.6")
+@nox.session(python="3.7")
 def lint(session):
     """Run linters.
 
@@ -126,4 +126,4 @@ def docs(session):
         os.path.join("docs", "_build", "doctrees", ""),
         os.path.join("docs", ""),
         os.path.join("docs", "_build", "html", ""),
-    )
+    )

api_core/tests/unit/test_operation.py

@@ -15,11 +15,10 @@
 
 import mock
 
+from google.api_core import exceptions
 from google.api_core import operation
 from google.api_core import operations_v1
 from google.api_core import retry
-from google.api_core import exceptions
-from google.api_core.future import polling
 from google.longrunning import operations_pb2
 from google.protobuf import struct_pb2
 from google.rpc import code_pb2