Conflict with CarrierWave/Fog/S3 remote_image_url method

[agdelarue]

Gemfile:
gem 'carrierwave', '0.6.2'
gem 'fog', '1.3.1', require: false
gem 'aws-s3', '0.6.3'
gem 'ruby-units', '1.4.3' (same with 1.4.2)
(...)

Define a model (say Product) with an 'image' field mounted to a simple CarrierWave uploader. Setup CarrierWave to use :fog as its config.storage with 'AWS' as the provider.

When you do "product.remote_image_url = some_http_url" pointing to a valid S3 image resource, it fails. The image is supposed to be copied from S3 to local storage and then processed by the uploader, but that doesn't happen anymore. There's a 'silent' error because mini_magick tries to process the local copy of the image, but that image is missing (mini_magick20130614-41738-19jua5l.jpg below doesn't exist on the filesystem).

If I remove 'ruby-units' from my gemfile everything is fine. Very strange. Note that in my console based use case I'm not using anything from ruby-units. ruby-units is only used in one of my view helpers.

Console:

p = Product.last
p.remote_image_url = some_http_S3_url_to_a_valid_image
Console output:
CarrierWave::ProcessingError: Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: Command ("mogrify -resize "921/2x307" /var/folders/wm/5v1yzyfx6v9dmjbl7416xq7r0000gn/T/mini_magick20130614-41738-19jua5l.jpg") failed: {:status_code=>1, :output=>"mogrify: invalid geometry 921/2x307' @ error/geometry.c/ParseRegionGeometry/1505.\n"} from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/processing/mini_magick.rb:250:inrescue in manipulate!'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/processing/mini_magick.rb:244:in manipulate!' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/processing/mini_magick.rb:145:inresize_to_fit'
from /Volumes/x/app/uploaders/base_uploader.rb:60:in do_resize' from /Volumes/x/app/uploaders/base_uploader.rb:37:inblock in resize_and_crop'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/processing/mini_magick.rb:246:in manipulate!' from /Volumes/x/app/uploaders/base_uploader.rb:36:inresize_and_crop'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/processing.rb:85:in block in process!' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/processing.rb:81:ineach'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/processing.rb:81:in process!' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:inblock in with_callbacks'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:in each' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:inwith_callbacks'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/cache.rb:112:in cache!' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/versions.rb:231:inblock in cache_versions!'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/versions.rb:216:in each' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/versions.rb:216:incache_versions!'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:in block in with_callbacks' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:ineach'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/callbacks.rb:18:in with_callbacks' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/cache.rb:112:incache!'
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/uploader/download.rb:58:in download!' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/mount.rb:337:inremote_url='
from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/mount.rb:197:in remote_image_url=' from /Users/a/.rvm/gems/ruby-1.9.3-p429@z/gems/carrierwave-0.6.2/lib/carrierwave/orm/activerecord.rb:43:inremote_image_url='

[olbrich]

It's possible that something in your gems is not compatible with the 'mathn' library. Try removing ruby-units and then manually requiring 'mathn'. If it fails under those conditions then something in your toolchain is not compatible with 'mathn'.