$ rbenv install 2.5.0
$ gem install bundler
$ bundle update --source excon
Traceback (most recent call last):
2: from /home/zunda/.rbenv/versions/2.5.0/bin/bundle:23:in `<main>'
1: from /home/zunda/.rbenv/versions/2.5.0/lib/ruby/2.5.0/rubygems.rb:308:in `activate_bin_path'
/home/zunda/.rbenv/versions/2.5.0/lib/ruby/2.5.0/rubygems.rb:289:in `find_spec_for_exe': can't find gem bundler (>= 0.a) with executable bundle (Gem::GemNotFoundException)
どうするんだっけ…