title: cannot load such file -- readline (LoadError) when running heroku create --stack cedar
body: <p>I'm trying to deploy my Rails application to Heroku to test it out by following these instructions:</p>
  
  <p><a href="http://devcenter.heroku.com/articles/rails3#prerequisites" rel="noreferrer">http://devcenter.heroku.com/articles/rails3#prerequisites</a></p>
  
  <p>Here is the command I'm trying to run:</p>
  
  <pre><code>heroku create --stack cedar
  </code></pre>
  
  <p>And I get this error message:</p>
  
  <pre><code>/home/sergio/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- readline (LoadError)
      from /home/sergio/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/lib/heroku/command/run.rb:1:in `&lt;top (required)&gt;'
      from /home/sergio/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
      from /home/sergio/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/lib/heroku/command.rb:14:in `block in load'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/lib/heroku/command.rb:13:in `each'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/lib/heroku/command.rb:13:in `load'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/lib/heroku/cli.rb:8:in `start'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/gems/heroku-2.20.1/bin/heroku:15:in `&lt;top (required)&gt;'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/bin/heroku:19:in `load'
      from /home/sergio/.rvm/gems/ruby-1.9.3-p125/bin/heroku:19:in `&lt;main&gt;'
  </code></pre>
  
  <p>And this is the content of the file in question:</p>
  
  <pre><code>#--
  # Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
  # All rights reserved.
  # See LICENSE.txt for permissions.
  #++
  
  module Kernel
  
    if defined?(gem_original_require) then
      # Ruby ships with a custom_require, override its require
      remove_method :require
    else
      ##
      # The Kernel#require from before RubyGems was loaded.
  
      alias gem_original_require require
      private :gem_original_require
    end
  
    ##
    # When RubyGems is required, Kernel#require is replaced with our own which
    # is capable of loading gems on demand.
    #
    # When you call &lt;tt&gt;require 'x'&lt;/tt&gt;, this is what happens:
    # * If the file can be loaded from the existing Ruby loadpath, it
    #   is.
    # * Otherwise, installed gems are searched for a file that matches.
    #   If it's found in gem 'y', that gem is activated (added to the
    #   loadpath).
    #
    # The normal &lt;tt&gt;require&lt;/tt&gt; functionality of returning false if
    # that file has already been loaded is preserved.
  
    def require path
      if Gem.unresolved_deps.empty? then
        gem_original_require path
      else
        spec = Gem::Specification.find { |s|
          s.activated? and s.contains_requirable_file? path
        }
  
        unless spec then
          found_specs = Gem::Specification.find_in_unresolved path
          unless found_specs.empty? then
            found_specs = [found_specs.last]
          else
            found_specs = Gem::Specification.find_in_unresolved_tree path
          end
  
          found_specs.each do |found_spec|
            found_spec.activate
          end
        end
  
        return gem_original_require path
      end
    rescue LoadError =&gt; load_error
      if load_error.message.end_with?(path) and Gem.try_activate(path) then
        return gem_original_require(path)
      end
  
      raise load_error
    end
  
    private :require
  
  end
  </code></pre>
  
  <p>I can run my application locally using <code>rails -s</code>, but I just can't seem to publish it to Heroku.</p>