unused import, unused variable

Author: Jonathan Kliem

src/sage/geometry/polyhedron/base.py

@@ -9135,12 +9135,11 @@ def _test_is_combinatorially_isomorphic(self, tester=None, **options):
 
             sage: polytopes.cross_polytope(3)._test_is_combinatorially_isomorphic()
         """
-        from sage.rings.all import ZZ
         if tester is None:
             tester = self._tester(**options)
 
         if not self.is_compact():
-            with tester.assertRaises(AssertionError) as cm:
+            with tester.assertRaises(AssertionError):
                 self.is_combinatorially_isomorphic(self)
             return