fix error

Author: antgonza

qiita_pet/handlers/download.py

@@ -266,7 +266,7 @@ def get(self, extras):
         self.set_header('Content-Type', 'application/octet-stream')
         self.set_header('Content-Transfer-Encoding', 'binary')
         self.set_header('X-Accel-Redirect',
-                        '/protected-working_dir/' + relpath.decode('ascii'))
+                        f'/protected-working_dir/{relpath}')
         self.finish()