Issue #22599 changed tokenize.open() from using builtins.open() to having a module-level reference to _builtin_open, stored by doing _builtin_open = open. However, on reloading the module, _builtin_open is pointed to tokenize.open from the last execution of the code, breaking tokenize.open():

>>> import tokenize
>>> tokenize.open
<function open at 0x7f15b660fc80>
>>> tokenize._builtin_open
<built-in function open>
>>> import imp; imp.reload(tokenize)
<module 'tokenize' from '/home/takluyver/miniconda3/envs/py34/lib/python3.4/tokenize.py'>
>>> tokenize.open
<function open at 0x7f15b660fbf8>
>>> tokenize._builtin_open
<function open at 0x7f15b660fc80>
>>> tokenize.open('foo.py')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/takluyver/miniconda3/envs/py34/lib/python3.4/tokenize.py", line 438, in open
    buffer = _builtin_open(filename, 'rb')
TypeError: open() takes 1 positional argument but 2 were given

The actual case where I'm seeing this error is nose logging a failure in a test suite, so it's not clear what is reloading tokenize, but it appears that something is. This just started failing when our Windows test system updated to Python 3.4.3.

Patch attached to fix this.

The same issue exists in Lib/bz2.py, Lib/tarfile.py, Tools/freeze/bkfile.py.

May be write a code as

from builtins import open as _builtin_open

?

-B.patch as Serhiy suggests, for tokenize only for the time being.

LGTM. Do you want to write a patch for other cases Thomas?

Fixed the other three cases you pointed out (-B2.patch).

LGTM.

LGTM as well. You want to commit, Serhiy? If not assign to me and I will get to it on Friday.

New changeset 383ba3699084 by Serhiy Storchaka in branch '3.4':
Issue #23615: Modules bz2, tarfile and tokenize now can be reloaded with
https://hg.python.org/cpython/rev/383ba3699084

New changeset 6e736a57a482 by Serhiy Storchaka in branch 'default':
Issue #23615: Modules bz2, tarfile and tokenize now can be reloaded with
https://hg.python.org/cpython/rev/6e736a57a482

New changeset 36bd5add9732 by Serhiy Storchaka in branch '2.7':
Issue #23615: Module tarfile is now can be reloaded with imp.reload().
https://hg.python.org/cpython/rev/36bd5add9732

Is there a method to detect other reload bugs?

Only grep.