Add missing imports from typing (#933)

third_party/2and3/boto/s3/bucket.pyi

@@ -6,7 +6,7 @@ from .bucketlistresultset import BucketListResultSet
 from .connection import S3Connection
 from .key import Key
 
-from typing import Any, Dict, Optional, Text, Type
+from typing import Any, Dict, Optional, Text, Type, List
 
 class S3WebsiteEndpointTranslate:
     trans_region = ...  # type: Dict[str, str]

third_party/2and3/sqlalchemy/sql/schema.pyi

@@ -1,4 +1,4 @@
-from typing import Any, AnyStr
+from typing import Any, AnyStr, Set
 
 from .base import SchemaEventTarget, DialectKWArgs
 from .base import ColumnCollection