gistfile1.txt

$ bundle install
Fetching gem metadata from https://rubygems.org/..........
Resolving dependencies...
Bundler found conflicting requirements for the Ruby version:
  In Gemfile:
    Ruby

    asciidoctor-epub3 (= 1.5.0.alpha.19) was resolved to 1.5.0.alpha.19, which depends on
      Ruby (>= 2.3.0)

    html-proofer (= 3.19.0) was resolved to 3.19.0, which depends on
      Ruby (< 4.0, >= 2.4.10)

    asciidoctor-pdf (= 1.5.4) was resolved to 1.5.4, which depends on
      prawn (~> 2.2.0) was resolved to 2.2.2, which depends on
        Ruby (~> 2.1)

    asciidoctor-pdf (= 1.5.4) was resolved to 1.5.4, which depends on
      prawn-svg (~> 0.31.0) was resolved to 0.31.0, which depends on
        Ruby (>= 2.1.0)
        
$ ruby -v 
ruby 3.0.1p64 (2021-04-05 revision 0fb782ee38) [x86_64-linux]