These are repro instructions for

• matthewwithanm/django-imagekit#369.
• etianen/django-s3-storage#33

UPDATE: this is now fixed! The fix was in django-s3-storage.

S3 prep

First, create a new s3 bucket (ours is named iktest-media in this example). We'll need your access keys and bucket name available in your environment later, so go ahead and just export them now:

$ export AWS_ACCESS_KEY_ID=...
$ export AWS_SECRET_ACCESS_KEY=...
$ export AWS_S3_BUCKET_NAME=iktest-media  # replace with your bucket name

Now clone the iktest repo:

$ git clone https://github.com/mgalgs/iktest.git
$ cd iktest

and upload the IMG_20160609_183718.jpg file from this repo to your new bucket:

$ aws s3 cp IMG_20160609_183718.jpg s3://iktest-media/media/test_images/

Your bucket should now look like this:

$ aws s3 ls --recursive s3://iktest-media
2016-08-11 20:03:26      49093 media/test_images/IMG_20160609_183718.jpg

Django prep

Install everything in a fresh virtualenv and bootstrap some data:

$ virtualenv env
$ . env/bin/activate
$ pip install Django==1.9 django-s3-storage Pillow git+git://github.com/matthewwithanm/django-imagekit.git@develop
$ python manage.py migrate
$ python manage.py testdata

Running the app

You're now ready to run the dev server:

$ python manage runserver

Load http://localhost:8000 in your web browser. You'll notice that the first time you load the page it will complain with:

Internal Server Error: /
Traceback (most recent call last):
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/mgalgs/sites/iktest2/iktest/testapp/views.py", line 10, in index_view
    'widgets': TestWidget.objects.all(),
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/shortcuts.py", line 67, in render
    template_name, context, request=request, using=using)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/loader.py", line 97, in render_to_string
    return template.render(context, request)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/backends/django.py", line 95, in render
    return self.template.render(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 206, in render
    return self._render(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 197, in _render
    return self.nodelist.render(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 988, in render
    bit = node.render_annotated(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 955, in render_annotated
    return self.render(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/defaulttags.py", line 220, in render
    nodelist.append(node.render_annotated(context))
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 955, in render_annotated
    return self.render(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 1039, in render
    output = self.filter_expression.resolve(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 705, in resolve
    obj = self.var.resolve(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 846, in resolve
    value = self._resolve_lookup(context)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/template/base.py", line 887, in _resolve_lookup
    current = getattr(current, bit)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/__init__.py", line 84, in url
    return self._storage_attr('url')
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/__init__.py", line 74, in _storage_attr
    existence_required.send(sender=self, file=self)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 192, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/registry.py", line 53, in existence_required_receiver
    self._receive(file, 'on_existence_required')
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/registry.py", line 61, in _receive
    call_strategy_method(file, callback)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/utils.py", line 148, in call_strategy_method
    fn(file)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/strategies.py", line 15, in on_existence_required
    file.generate()
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/__init__.py", line 93, in generate
    self.cachefile_backend.generate(self, force)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/backends.py", line 108, in generate
    self.generate_now(file, force=force)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/backends.py", line 95, in generate_now
    file._generate()
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/cachefiles/__init__.py", line 97, in _generate
    content = generate(self.generator)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/utils.py", line 134, in generate
    content = generator.generate()
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/imagekit/specs/__init__.py", line 153, in generate
    self.source.open()
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/db/models/fields/files.py", line 81, in open
    self.file.open(mode)
  File "/home/mgalgs/sites/iktest2/env/lib/python2.7/site-packages/django/core/files/base.py", line 141, in open
    raise ValueError("The file cannot be reopened.")
ValueError: The file cannot be reopened.

If you reload your page it will work(!). However, the thumbnails that got generated won't actually be valid. Compare the urls from your web browser to:

$ aws s3 ls --recursive s3://iktest-media