Issue #23615: Modules bz2, tarfile and tokenize now can be reloaded with
imp.reload().  Patch by Thomas Kluyver.
diff --git a/Tools/freeze/bkfile.py b/Tools/freeze/bkfile.py
index 58246fa..6abacc9 100644
--- a/Tools/freeze/bkfile.py
+++ b/Tools/freeze/bkfile.py
@@ -1,4 +1,4 @@
-_orig_open = open
+from builtins import open as _orig_open
 
 class _BkFile:
     def __init__(self, file, mode, bufsize):