typo in sessions file backend can cause NameError

fix typo in contrib/sessions/file.py

This can't be correct. The errno has existed at the top level since of Python, approximately, forever. And os.errno does not exist in normal Python. So you'll need to supply a few more details here about what type of system you're running on and Python you're using, because it sounds very non-standard.

Sorry, I didn't realize errno was available as a top-level import. The bug still exists, but in that case a just-as-good fix would be to import errno at the top of contrib/sessions/backends/file.py. It currently is not imported and I am definitely able to raise a NameError?. On SVN r8449, set SESSION_FILE_PATH = '/', run "./manage.py shell":

>>> from django.contrib.sessions.backends.file import SessionStore; SessionStore().create()
Traceback (most recent call last):
  File "<console>", line 1, in ?
  File "/var/www/meyer/lib/py/django/contrib/sessions/backends/file.py", line 6e
    self.save(must_create=True)
  File "/var/www/meyer/lib/py/django/contrib/sessions/backends/file.py", line 8e
    if must_create and e.errno == errno.EEXIST:
NameError: global name 'errno' is not defined

My fix also works; os.errno does exist:

carljm@arugula:~$ python
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52) 
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.errno
<module 'errno' (built-in)>
>>> os.errno.EEXIST
17

There's nothing nonstandard about my setup, Python 2.5.2 straight from the Ubuntu repos.

Ah, checking on Python 2.4 reveals there's no os.errno there; so clearly importing toplevel errno is the better fix.

(In [8451]) Fixed #8457 -- Fixed a missing import.