Use the keyword form of file() instead of open() to create TESTFN.

Lib/test/test_descr.py

@@ -1671,7 +1671,7 @@ def inherits():
                 self.ateof = 1
             return s
 
-    f = open(TESTFN, 'w')
+    f = file(name=TESTFN, mode='w')
     lines = ['a\n', 'b\n', 'c\n']
     try:
         f.writelines(lines)