bpo-37999: No longer use __int__ in implicit integer conversions. (GH-15636)

Only __index__ should be used to make integer conversions lossless.
diff --git a/Lib/test/test_grp.py b/Lib/test/test_grp.py
index e511947..0993f09 100644
--- a/Lib/test/test_grp.py
+++ b/Lib/test/test_grp.py
@@ -100,8 +100,8 @@
             self.skipTest('no groups')
         # Choose an existent gid.
         gid = entries[0][2]
-        self.assertWarns(DeprecationWarning, grp.getgrgid, float(gid))
-        self.assertWarns(DeprecationWarning, grp.getgrgid, str(gid))
+        self.assertRaises(TypeError, grp.getgrgid, float(gid))
+        self.assertRaises(TypeError, grp.getgrgid, str(gid))
 
 
 if __name__ == "__main__":