Fix pre-commit.

jazzband/db.py

@@ -1,12 +1,7 @@
-from collections import deque
-from contextlib import contextmanager
-
 from flask_redis import FlaskRedis
 from flask_sqlalchemy import Model, SQLAlchemy
 from walrus import Walrus
 
-from .exceptions import Rollback
-
 
 class JazzbandModel(Model):
     @classmethod