Fix the formatting

Now that the changes to lint.yml are fixed up, tested, and shown
to be capable of revealing formatting errors, the formatting error
I was using for testing (which is from 9fa1cee where I had
introduced it inadvertently) can be fixed.

test/test_git.py

@@ -43,7 +43,7 @@ def tearDown(self):
     def _assert_logged_for_popen(self, log_watcher, name, value):
         re_name = re.escape(name)
         re_value = re.escape(str(value))
-        re_line = re.compile(fr"DEBUG:git.cmd:Popen\(.*\b{re_name}={re_value}[,)]")
+        re_line = re.compile(rf"DEBUG:git.cmd:Popen\(.*\b{re_name}={re_value}[,)]")
         match_attempts = [re_line.match(message) for message in log_watcher.output]
         self.assertTrue(any(match_attempts), repr(log_watcher.output))