[tests] use f-strings (##7671)

test/test_job.py

@@ -299,7 +299,7 @@ class TestDataJob(TestJob):
         for i in range(1, 4):
             self.assertEqual(
                 tjob.data[i][2]["_fallback"],
-                ("https://example.org/alt/{}.jpg".format(i),),
+                (f"https://example.org/alt/{i}.jpg",),
             )
 
     def test_sleep(self):
@@ -382,13 +382,13 @@ class TestExtractor(Extractor):
         }
 
         for i in range(1, 4):
-            url = "{}/{}.jpg".format(root, i)
+            url = f"{root}/{i}.jpg"
             yield Message.Url, url, text.nameext_from_url(url, {
                 "num" : i,
                 "tags": ["foo", "bar", "テスト"],
                 "user": user,
                 "author": user,
-                "_fallback": ("{}/alt/{}.jpg".format(root, i),),
+                "_fallback": (f"{root}/alt/{i}.jpg",),
             })