no-issue: remove unused import from test_graphlib.py (GH-29853)

Author: adriangb

Lib/test/test_graphlib.py

@@ -1,4 +1,3 @@
-from itertools import chain
 import graphlib
 import os
 import unittest
@@ -34,7 +33,7 @@ def _assert_cycle(self, graph, cycle):
         try:
             ts.prepare()
         except graphlib.CycleError as e:
-            msg, seq = e.args
+            _, seq = e.args
             self.assertIn(" ".join(map(str, cycle)), " ".join(map(str, seq * 2)))
         else:
             raise