[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/postgres_tests/test_constraints.py

@@ -300,8 +300,9 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
     def test_empty_expressions(self):
         msg = "At least one expression is required to define an exclusion constraint."
         for empty_expressions in (None, []):
-            with self.subTest(empty_expressions), self.assertRaisesMessage(
-                ValueError, msg
+            with (
+                self.subTest(empty_expressions),
+                self.assertRaisesMessage(ValueError, msg),
             ):
                 ExclusionConstraint(
                     index_type="GIST",