ruby on rails - No such file or directory - convert -

i'm new rails. today i've started have issues related nokogiri , digest md5. when ran rails s app contribute to, started complain, first nokogiri not being installed , digest md5.

discourse git:(after-hook-event) ✗ bundle install /users/jlijo/.rvm/rubies/ruby-2.4.0-turbo/lib/ruby/2.4.0/digest.rb:16:in `const_missing': library not found class digest::md5 -- digest/md5 (loaderror) 

i've fixed issue nokogiri doing xcode-select --install . console stopped complain digest md5 still app won't work (even tho, rails server starts), raises error:

digest::md5.hexdigest(`convert --version` << `convert -list font`)  undefined method `<<' nil:nilclass 

this rather desperating, i've spent whole afternoon trying solve issue. don't know root of it. i've reinstalled ruby 2.4.0 again. i've ran gem install bundler, , bundle install.

logs:

 d, [2017-08-18t19:28:22.945251 #64797] debug -- :   themefield load (1.3ms)  select "theme_fields".* "theme_fields" join (           select 2 theme_id, 0 sort_column         ) x on x.theme_id = theme_fields.theme_id "theme_fields"."target_id" in (1, 0) , "theme_fields"."name" = 'header'  order sort_column, target_id  [["name", "header"]] bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert i, [2017-08-18t19:28:22.973323 #64797]  info -- :   rendered common/_discourse_javascript.html.erb (22.8ms) i, [2017-08-18t19:28:22.975885 #64797]  info -- : completed 500 internal server error in 683ms (activerecord: 98.6ms) f, [2017-08-18t19:28:22.994012 #64797] fatal -- : nomethoderror - undefined method `<<' nil:nilclass:   lib/letter_avatar.rb:103:in `image_magick_version'   lib/letter_avatar.rb:26:in `version'   app/views/common/_discourse_javascript.html.erb:44:in `_app_views_common__discourse_javascript_html_erb___995238869359027967_70217684279780'   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railties (4.2.9) lib/rails/engine.rb:518:in `call'   railties (4.2.9) lib/rails/application.rb:165:in `call'   railties (4.2.9) lib/rails/railtie.rb:194:in `method_missing'   rack (1.6.8) lib/rack/urlmap.rb:66:in `block in call'   rack (1.6.8) lib/rack/urlmap.rb:50:in `call'   rack (1.6.8) lib/rack/content_length.rb:15:in `call'   puma (3.9.1) lib/puma/configuration.rb:224:in `call'   puma (3.9.1) lib/puma/server.rb:602:in `handle_request'   puma (3.9.1) lib/puma/server.rb:435:in `process_client'   puma (3.9.1) lib/puma/server.rb:299:in `block in run'   puma (3.9.1) lib/puma/thread_pool.rb:120:in `block in spawn_thread'  d, [2017-08-18t19:28:23.107322 #64797] debug -- : d, [2017-08-18t19:28:23.107454 #64797] debug -- : i, [2017-08-18t19:28:23.107604 #64797]  info -- : started post "/__better_errors/5a9496d634c72ab8/variables" ::1 @ 2017-08-18 19:28:23 +0200 bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert bin/rails: no such file or directory - convert 

you might not have imagemagick installed, convert command comes from. error out , leave nil.