Issue #23615: Modules bz2, tarfile and tokenize now can be reloaded with
imp.reload().  Patch by Thomas Kluyver.
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 37e4dcd..f9e5c18 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -38,6 +38,7 @@
 #---------
 # Imports
 #---------
+from builtins import open as bltn_open
 import sys
 import os
 import io
@@ -2421,7 +2422,6 @@
     except TarError:
         return False
 
-bltn_open = open
 open = TarFile.open