Issue #11074: Make 'tokenize' so it can be reloaded.

The module stored away the 'open' object as found in the global namespace
(which fell through to the built-in namespace) since it defined its own 'open'.
Problem is that if you reloaded the module it then grabbed the 'open' defined
in the previous load, leading to code that infinite recursed. Switched to
simply call builtins.open directly.

Lib/tokenize.py

@@ -24,6 +24,7 @@ __author__ = 'Ka-Ping Yee <ping@lfw.org>'
 __credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
                'Skip Montanaro, Raymond Hettinger, Trent Nelson, '
                'Michael Foord')
+import builtins
 import re
 import sys
 from token import *
@@ -335,13 +336,11 @@ def detect_encoding(readline):
     return default, [first, second]
 
 
-_builtin_open = open
-
 def open(filename):
     """Open a file in read only mode using the encoding detected by
     detect_encoding().
     """
-    buffer = _builtin_open(filename, 'rb')
+    buffer = builtins.open(filename, 'rb')
     encoding, lines = detect_encoding(buffer.readline)
     buffer.seek(0)
     text = TextIOWrapper(buffer, encoding, line_buffering=True)