[5.0.x] Applied Black's 2024 stable style.

https://github.com/psf/black/releases/tag/24.1.0

Backport of 305757aec1 from main

tests/test_client/tests.py

@@ -19,6 +19,7 @@ testing against the contexts and templates produced by a view,
 rather than the HTML rendered to the end-user.
 
 """
+
 import copy
 import itertools
 import tempfile