install_serially

# File lib/bundler/installer/parallel_installer.rb, line 144
    def install_serially
      until finished_installing?
        raise "failed to find a spec to enqueue while installing serially" unless spec_install = @specs.find(&:ready_to_enqueue?)
        spec_install.state = :enqueued
        do_install(spec_install, 0)
      end
    end