style: format backend with black

Also drops the session-sliding comment in login_required.

backend/tests/__init__.py

@@ -1,10 +1,13 @@
 """Point the app at a dedicated test database before any test module imports it."""
+
 import os
 
 import psycopg2
 from psycopg2 import sql
 
-ADMIN_URL = os.environ.get("TEST_ADMIN_DATABASE_URL", "postgresql://postgres:[email protected]:5432/postgres")
+ADMIN_URL = os.environ.get(
+    "TEST_ADMIN_DATABASE_URL", "postgresql://postgres:[email protected]:5432/postgres"
+)
 TEST_DATABASE = "books_test"
 
 
@@ -13,9 +16,13 @@ def _ensure_test_database() -> None:
     conn.autocommit = True  # CREATE DATABASE cannot run inside a transaction
     try:
         with conn.cursor() as cur:
-            cur.execute("SELECT 1 FROM pg_database WHERE datname = %s", (TEST_DATABASE,))
+            cur.execute(
+                "SELECT 1 FROM pg_database WHERE datname = %s", (TEST_DATABASE,)
+            )
             if cur.fetchone() is None:
-                cur.execute(sql.SQL("CREATE DATABASE {}").format(sql.Identifier(TEST_DATABASE)))
+                cur.execute(
+                    sql.SQL("CREATE DATABASE {}").format(sql.Identifier(TEST_DATABASE))
+                )
     finally:
         conn.close()