ruby-on-rails – 在heroku上执行恶毒pdf的问题

我正在使用 this guide将wicked_pdf整合到heroku上.但不知何故它似乎不起作用.我得到了英雄的日志,它说：

Processing PdfController#get_pdf to pdf (for 115.248.175.50 at 2011-02-15 23:54:44) [GET]
  Parameters: {"format"=>"pdf","action"=>"get_pdf","id"=>"1","controller"=>"pdf"}
***************WICKED***************
Rendering pdf/get_pdf

RuntimeError (PDF could not be generated!
/usr/ruby1.8.7/lib/ruby/1.8/open3.rb:73:in `exec': No such file or directory - /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/bin/wkhtmltopdf-amd64       - -  (Errno::ENOENT)
    from /usr/ruby1.8.7/lib/ruby/1.8/open3.rb:73:in `popen3'
    from /usr/ruby1.8.7/lib/ruby/1.8/open3.rb:59:in `fork'
    from /usr/ruby1.8.7/lib/ruby/1.8/open3.rb:59:in `popen3'
    from /usr/ruby1.8.7/lib/ruby/1.8/open3.rb:57:in `fork'
    from /usr/ruby1.8.7/lib/ruby/1.8/open3.rb:57:in `popen3'
    from /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/vendor/plugins/wicked_pdf/lib/wicked_pdf.rb:22:in `pdf_from_string'
    from /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/vendor/plugins/wicked_pdf/lib/pdf_Helper.rb:28:in `make_pdf'
    from /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/vendor/plugins/wicked_pdf/lib/pdf_Helper.rb:39:in `make_and_send_pdf'
    from /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/vendor/plugins/wicked_pdf/lib/pdf_Helper.rb:13:in `render'
    from /app/fa369291-829b-4b61-9efe-b2f0d0a0a42c/home/app/controllers/schedule_controller.rb:33:in `get_pdf'

请帮忙.提前致谢.

编辑：

我在代码中做了一些修改,并通过这个错误,但仍然停留在这里

NoMethodError(未定义的方法为空？for#< Pathname：0x2b7112392480>)