rubocopがエラーになる（`require': cannot load such file -- rubocop-rspec）

エラー内容

$ rubocop

/Users/user_name/.rbenv/versions/2.3.1/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- rubocop-rspec (LoadError)
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_loader_resolver.rb:15:in `block in resolve_requires'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_loader_resolver.rb:11:in `each'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_loader_resolver.rb:11:in `resolve_requires'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_loader.rb:40:in `load_file'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_loader.rb:105:in `configuration_from_file'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/config_store.rb:44:in `for'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/cli.rb:93:in `apply_default_formatter'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/lib/rubocop/cli.rb:25:in `run'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/bin/rubocop:13:in `block in <top (required)>'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/2.3.0/benchmark.rb:308:in `realtime'
  from /Users/user_name/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rubocop-0.46.0/bin/rubocop:12:in `<top (required)>'
  from /Users/user_name/.rbenv/versions/2.3.1/bin/rubocop:23:in `load'
  from /Users/user_name/.rbenv/versions/2.3.1/bin/rubocop:23:in `<main>'

解決策

.rubocop.ymlの

require: rubocop-rspec

という記述を以下に変更する

AllCops:
  Include:
    - rubocop-rspec

Thanks

version

$ ruby -v
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin15]

$ rubocop -v
0.46.0