refactor: convert remaining percent formatting in log messages

gns3server/logger.py

@@ -125,8 +125,8 @@ class CompressedRotatingFileHandler(RotatingFileHandler):
             self.stream.close()
         if self.backupCount > 0:
             for i in range(self.backupCount - 1, 0, -1):
-                sfn = "%s.%d.gz" % (self.baseFilename, i)
-                dfn = "%s.%d.gz" % (self.baseFilename, i + 1)
+                sfn = f"{self.baseFilename}.{i}.gz"
+                dfn = f"{self.baseFilename}.{i + 1}.gz"
                 if os.path.exists(sfn):
                     if os.path.exists(dfn):
                         os.remove(dfn)