Rails - Carrierwave process throws ArgumentError: no images in this image list

Question

After attempting to implement a process to apply auto_orient! to my images I am getting this error:

ArgumentError (no images in this image list):
  app/uploaders/image_uploader.rb:36:in `fix_exif_rotation'
  app/controllers/posts_controller.rb:12:in `create'

Carrierwave works fine without the process but throws an error when I try to upload images after adding the process. Here's the process:

  process :fix_exif_rotation

  def fix_exif_rotation
    manipulate! do |image|
      image = image.auto_orient!
    end
  end

And here is my posts#create:

  def create
    @user = User.find(current_user.id)
    @post = @user.posts.create(params[:post].permit(:text, :image))
    redirect_to user_path(@user)
  end

Answer 1

I got the same error, and fixed it by installing ghostscript

brew install ghostscript