Issue 44 - rietveld - Django fails to load on Windows with "AttributeError: 'module' object has no attribute 'unlink'"

Issue 44:	Django fails to load on Windows with "AttributeError: 'module' object has no attribute 'unlink'"	‹ Prev 3 of 51 Next ›
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Status:	New
Owner:	----
Type-Defect
Priority-Medium

Reported by michael.hart.au, Sep 15, 2008

What steps will reproduce the problem?

1. Install Python 2.5.2 on Windows (XP in my case)
2. Setup PATHs, etc for GAE
3. Run rietveld.py serve (or any other method of starting rietveld)
4. Navigate to http://localhost:<port>/


What is the expected output? What do you see instead?

I expect it to load the Issues list as per normal.
Instead, I get the exception as listed in the Issue summary


What version of the product are you using? On what operating system?

GAE 1.1.2, latest trunk of rietveld (revision 311)


Please provide any additional information below.

Basically it's due to Django's use of os.unlink in 
django/core/files/temp.py, line 34

When the django module is imported in rietveld/main.py, this line throws 
because os.unlink is not available in GAE.

This could be solved either by patching Django to check for the existence 
of os.unlink (arguably a bit overkill for such an obscure situation), or by 
making it a noop in rietveld.

Attached is a patch for the latter. This solves the issue for me.

make_unlink_noop.patch
526 bytes Download

Comment 1 by michael.hart.au, Sep 15, 2008

Just confirmed this still occurs in GAE 1.1.3

Comment 2 by gvanrossum, Sep 16, 2008

Please report this to the Django folks.  They would like to be able to run without a
writable filesystem.

I suspect that if you patch os.unlink() to be a no-op, something else will fail,
because it's probably unlinking in anticipation of writing a temp file, which will
also fail...

Comment 3 by michael.hart.au, Sep 16, 2008

OK, no probs - I'm not sure of the best way to go about it - just checking for the 
presence (or lack thereof) of os.unlink works fine, but I don't know if there's a 
better way to deal with a non-writable filesystem as a whole.

I've created a ticket (and patch) at Django here:

http://code.djangoproject.com/ticket/9115

Comment 5 by jayeshsalvi, Oct 23, 2008

I am trying to write a webapp which does an urllib.urlopen to an outside URL. And as
it appears, urllib - like django - tries to use os.unlink. here is part of the stack
trace:


f = urllib.urlopen(self.fURL,postData)
File "/usr/lib64/python2.5/urllib.py", line 77, in urlopen
opener = FancyURLopener()
File "/usr/lib64/python2.5/urllib.py", line 609, in __init__
URLopener.__init__(self, *args, **kwargs)
File "/usr/lib64/python2.5/urllib.py", line 123, in __init__
self.__unlink = os.unlink # See cleanup()
AttributeError: 'module' object has no attribute 'unlink'

Comment 6 by gvanrossum, Oct 24, 2008

@jayeshsalvi - don't use urllib, use google.appengine.api.urlfetch.  See
http://code.google.com/appengine/docs/urlfetch/

Comment 7 by jayeshsalvi, Oct 24, 2008

@gvanrossum - Thanks a lot. That works for me.

Comment 8 by guiyang...@gmail.com, Jan 13, 2009

Here we go! as attach!

temp.py
2.1 KB Download

Comment 9 by gvanrossum, Jan 13, 2009

@guiyang923: Sorry, we can't accept patches to Django here.  Please comment on the
Django ticket already created: http://code.djangoproject.com/ticket/9115