Fix flake8 failures

moto/backends.py

@@ -60,6 +60,7 @@ BACKENDS = {
     'datapipeline': datapipeline_backends,
     'dynamodb': dynamodb_backends,
     'dynamodb2': dynamodb_backends2,
+    'dynamodbstreams': dynamodbstreams_backends,
     'ec2': ec2_backends,
     'ecr': ecr_backends,
     'ecs': ecs_backends,

moto/dynamodb2/models.py

@@ -1,5 +1,5 @@
 from __future__ import unicode_literals
-from collections import defaultdict, namedtuple
+from collections import defaultdict
 import copy
 import datetime
 import decimal

moto/dynamodbstreams/models.py

@@ -4,7 +4,6 @@ import os
 import json
 import boto3
 import base64
-import datetime
 
 from moto.core import BaseBackend, BaseModel
 from moto.dynamodb2.models import dynamodb_backends
@@ -124,7 +123,6 @@ class DynamoDBStreamsBackend(BaseBackend):
         return json.dumps(shard_iterator.get(limit))
 
 
-
 available_regions = boto3.session.Session().get_available_regions(
     'dynamodbstreams')
 dynamodbstreams_backends = {region: DynamoDBStreamsBackend(region=region)

moto/dynamodbstreams/responses.py

@@ -1,7 +1,5 @@
 from __future__ import unicode_literals
 
-import json
-
 from moto.core.responses import BaseResponse
 
 from .models import dynamodbstreams_backends