ruby-default-gems have to depend on rubygem(io-console) due to reline.
    
    This fixes IRB failures:
    
    ~~~
    $ irb
    /usr/share/rubygems/rubygems/specification.rb:1398:in `rescue in block in activate_dependencies': Could not find 'io-console' (~> 0.5) among 76 total gem(s) (Gem::MissingSpecError)
    Checked in 'GEM_PATH=/builddir/.local/share/gem/ruby:/usr/share/gems:/usr/local/share/gems' at: /usr/share/gems/specifications/reline-0.2.0.gemspec, execute `gem env` for more information
    	from /usr/share/rubygems/rubygems/specification.rb:1395:in `block in activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `each'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1366:in `activate'
    	from /usr/share/rubygems/rubygems/specification.rb:1402:in `block in activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `each'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1366:in `activate'
    	from /usr/share/rubygems/rubygems.rb:302:in `block in activate_bin_path'
    	from /usr/share/rubygems/rubygems.rb:301:in `synchronize'
    	from /usr/share/rubygems/rubygems.rb:301:in `activate_bin_path'
    	from /usr/bin/irb:23:in `<main>'
    /usr/share/rubygems/rubygems/dependency.rb:307:in `to_specs': Could not find 'io-console' (~> 0.5) among 76 total gem(s) (Gem::MissingSpecError)
    Checked in 'GEM_PATH=/builddir/.local/share/gem/ruby:/usr/share/gems:/usr/local/share/gems' , execute `gem env` for more information
    	from /usr/share/rubygems/rubygems/specification.rb:1396:in `block in activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `each'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1366:in `activate'
    	from /usr/share/rubygems/rubygems/specification.rb:1402:in `block in activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `each'
    	from /usr/share/rubygems/rubygems/specification.rb:1384:in `activate_dependencies'
    	from /usr/share/rubygems/rubygems/specification.rb:1366:in `activate'
    	from /usr/share/rubygems/rubygems.rb:302:in `block in activate_bin_path'
    	from /usr/share/rubygems/rubygems.rb:301:in `synchronize'
    	from /usr/share/rubygems/rubygems.rb:301:in `activate_bin_path'
    	from /usr/bin/irb:23:in `<main>'
    ~~~