This is very annoying because it happened right in the middle of upgrading a system from 1.4 to next:

>>> Emerging (1 of 70) dev-ruby/racc-1.6.2::ruby-kit

• racc-1.6.2-8d1c1ed.tar.gz BLAKE2B SHA512 size ... [ ok ]
  >>> Unpacking source...
• Running unpack phase for all ...
  >>> Unpacking racc-1.6.2-8d1c1ed.tar.gz to /var/tmp/portage/dev-ruby/racc-1.6.2/work/all
  >>> Source unpacked in /var/tmp/portage/dev-ruby/racc-1.6.2/work
  >>> Preparing source in /var/tmp/portage/dev-ruby/racc-1.6.2/work ...
• Running prepare phase for all ...
• Running prepare phase for all ...
  /usr/lib64/ruby/2.6.0/rubygems.rb:16:in `require': cannot load such file – rubygems/compatibility (LoadError)
  from /usr/lib64/ruby/2.6.0/rubygems.rb:16:in `<top (required)>'
  from <internal:gem_prelude>:2:in `require'
  from <internal:gem_prelude>:2:in `<internal:gem_prelude>'
• ERROR: dev-ruby/racc-1.6.2::ruby-kit failed (prepare phase):
• (no error message)

I'm attaching the build.log. Because of that error I can't finish the upgrade.

• Call stack:
• ebuild.sh, line 93: Called src_prepare
• environment, line 2117: Called ruby-ng_src_prepare
• environment, line 1744: Called _ruby_invoke_environment 'all' '_ruby_apply_patches'
• environment, line 578: Called _ruby_apply_patches
• environment, line 402: Called all_ruby_prepare
• environment, line 680: Called die
• The specific snippet of code:
• rake lib/racc/parser-text.rb || die;