undefined method `plain_specs' for #<Bundler::RubygemsIntegration:0x00005633f09a9000> (NoMethodError)
gem uninstall rubygems-bundler
works for me I am using bundler 2.1.0
REF: https://github.com/bundler/bundler/issues/7492
When showing
ERROR: While executing gem ... (Gem::InstallError)
rubygems-bundler is not installed in GEM_HOME, try:
gem uninstall -i /Users/xxxx/.rvm/rubies/ruby-2.5.7/lib/ruby/gems/2.5.0 rubygems-bundler
Please run
gem uninstall -i /Users/xxxx/.rvm/rubies/ruby-2.5.7/lib/ruby/gems/2.5.0 rubygems-bundler