Rakefile in rubocop-rspec-1.18.0 vs Rakefile in rubocop-rspec-1.19.0

@@ -4,11 +4,11 @@
 require 'bundler/gem_tasks'
 
 begin
   Bundler.setup(:default, :development)
 rescue Bundler::BundlerError => e
-  $stderr.puts e.message
-  $stderr.puts 'Run `bundle install` to install missing gems'
+  warn e.message
+  warn 'Run `bundle install` to install missing gems'
   exit e.status_code
 end
 
 require 'rspec/core/rake_task'
 RSpec::Core::RakeTask.new(:spec) do |spec|