Upgrade to Red Hat Satellite 6.9 failing with Could not find rdoc (>= 3.9.0) among 229 total gem(s) (Gem::LoadError).

Issue

• Upgrade to Satellite 6.9 failing with below error.

  # satellite-maintain upgrade run --target-version 6.9
  
  /opt/rh/rh-ruby25/ doesn't exist
  /usr/bin/scl_source: line 63: /opt/rh/rh-ruby25/enable: No such file or directory
  Can't source enable, skipping.
  /usr/share/rubygems/rubygems/dependency.rb:296:in `to_specs': Could not find 'rdoc' (>= 3.9.0) among 229 total gem(s) (Gem::LoadError)
    from /usr/share/rubygems/rubygems/specification.rb:1212:in `block in activate_dependencies'
    from /usr/share/rubygems/rubygems/specification.rb:1201:in `each'
    from /usr/share/rubygems/rubygems/specification.rb:1201:in `activate_dependencies'
    from /usr/share/rubygems/rubygems/specification.rb:1183:in `activate'
    from /usr/share/rubygems/rubygems/specification.rb:1215:in `block in activate_dependencies'
    from /usr/share/rubygems/rubygems/specification.rb:1201:in `each'
    from /usr/share/rubygems/rubygems/specification.rb:1201:in `activate_dependencies'
    from /usr/share/rubygems/rubygems/specification.rb:1183:in `activate'
    from /usr/share/rubygems/rubygems.rb:186:in `rescue in try_activate'
    from /usr/share/rubygems/rubygems.rb:183:in `try_activate'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:132:in `rescue in require'
    from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:144:in `require'
    from /usr/sbin/satellite-installer:3:in `<main>'