Workaround for ubygems.rb / -rubygems parameter feature abruptly removed from Ruby. See https://bugs.ruby-lang.org/issues/14322

ubygems-workaround.sh

#!/bin/sh
# Copyright:: 2018 Daniel Barrows
# License::   zlib/libpng
# https://gist.github.com/daniel-barrows/ca8359b76ad9bb84b37593a9f7b695fc
#
# Workaround for feature abruptly removed from Ruby.
# See https://bugs.ruby-lang.org/issues/14322

# Leave warn variable empty to not output the deprecation warning.
warn=true
if ruby -e exit 2>&1 \
   | grep 'cannot load such file -- ubygems (LoadError)' >/dev/null; then
  which sudo >/dev/null 2>&1 && sudo=sudo
  ruby_lib_dir="$( ruby -e 'exit 0' 2>&1 | grep 'cannot load such file' \
                   | sed 's,/rubygems/core_ext.\+,,' )"
  if ! [ -z "$warn" ]; then
    warning_msg="warn 'WARNING: -rubygems flag is deprecated. Use -rrubygems.'"
  fi
  printf "#!/usr/bin/env ruby\n%s\nrequire 'rubygems'\n" "$warning_msg" \
  | $sudo tee "$ruby_lib_dir/ubygems.rb" > /dev/null
fi