Issue #23615: Modules bz2, tarfile and tokenize now can be reloaded with
imp.reload().  Patch by Thomas Kluyver.
diff --git a/Lib/bz2.py b/Lib/bz2.py
index 6f47bfa..6c5a60d 100644
--- a/Lib/bz2.py
+++ b/Lib/bz2.py
@@ -9,6 +9,7 @@
 
 __author__ = "Nadeem Vawda <nadeem.vawda@gmail.com>"
 
+from builtins import open as _builtin_open
 import io
 import warnings
 
@@ -27,8 +28,6 @@
 
 _BUFFER_SIZE = 8192
 
-_builtin_open = open
-
 
 class BZ2File(io.BufferedIOBase):