title: whenever gem error No such file or directory - crontab
body: <p>I dont know what problem is this.
  <a href="https://i.stack.imgur.com/PY3bE.png" rel="nofollow noreferrer">this my problem</a></p>
  
  <p>This is console output.</p>
  
  <pre><code>$ whenever --update-crontab
  Системе не удается найти указанный путь.
  C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:77:in `popen': No such file or directory - crontab - (Errno::ENOENT)
          from C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:77:in `write_crontab'
          from C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:38:in `run'
          from C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/whenever-0.10.0/lib/whenever/command_line.rb:6:in `execute'
          from C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/whenever-0.10.0/bin/whenever:44:in `&lt;top (required)&gt;'
          from C:/RailsInstaller/Ruby2.3.3/bin/whenever:22:in `load'
          from C:/RailsInstaller/Ruby2.3.3/bin/whenever:22:in `&lt;main&gt;'
  </code></pre>