[pre-commit.ci] auto fixes from pre-commit.com hooks

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t/unit/backends/test_redis.py

@@ -18,6 +18,7 @@
 from celery.utils.collections import AttributeDict
 from t.unit import conftest
 
+
 def raise_on_second_call(mock, exc, *retval):
     def on_first_call(*args, **kwargs):
         mock.side_effect = exc