title: wicked_pdf not working in production server
body: <p>Locally It works without any error but when I try to generate the PDF on the server it throws:</p>
  
  <pre><code> RuntimeError (Failed to execute:
      ["/usr/local/bin/wkhtmltopdf", "-q", "file:////tmp/wicked_pdf20180531-994-1x8fbfn.html", "/tmp/wicked_pdf_generated_file20180531-994-1vidmtk.pdf"]
      Error: PDF could not be generated!
  Command Error: /usr/bin/env: ruby: No such file or directory
  </code></pre>
  
  <p>Here's what's on <strong>my_controller</strong>.</p>
  
  <pre><code>pdf=WickedPdf.new.pdf_from_string(render_to_string('disc_bill',:layout=&gt;false))
    save_file = Rails.root.join("public","bill.pdf")
    File.open(save_file, 'wb') do |file|
      file &lt;&lt; pdf
    end
  </code></pre>
  
  <p>And in my <strong>Gemfile</strong></p>
  
  <pre><code>gem 'wicked_pdf', '~&gt; 1.1'
  gem 'wkhtmltopdf-binary', '~&gt; 0.12.3.1'
  </code></pre>