Fix for tet_bigmem.py (the failure was caused by a spurious reference

to 'file', which no longer exists).
Fix inspired by Christian Heimes, SF# 1752195.

Lib/test/test_bigmem.py

@@ -850,7 +850,7 @@ class ListTest(unittest.TestCase):
         self.assertEquals(l.count("1"), 0)
 
     def basic_test_extend(self, size):
-        l = [file] * size
+        l = [object] * size
         l.extend(l)
         self.assertEquals(len(l), size * 2)
         self.failUnless(l[0] is l[-1])